Three-dimensional printing with reciprocal feeding of polymerizable  liquid

ABSTRACT

Described herein are methods and apparatus for the production of a three-dimensional object by “bottom up” additive manufacturing, in which a carrier ( 112 ) is vertically reciprocated with respect to a build surface, to enhance or speed the refilling of the build region with a solidifiable liquid. In preferred embodiments, the three-dimensional object is produced from a liquid interface by continuous liquid interface production (i.e., “CLIP”).

RELATED APPLICATIONS

This application claims the benefit of United States Provisional PatentApplication Ser. No. 62/117,640, filed Feb. 18, 2015, 62/035,643, filedAug. 11, 2014, and 62/015,119, filed Jun. 20, 2014, the disclosures ofwhich are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention concerns methods and apparatus for the fabricationof solid three-dimensional objects from liquid materials.

BACKGROUND OF THE INVENTION

In conventional additive or three-dimensional fabrication techniques,construction of a three-dimensional object is performed in a step-wiseor layer-by-layer manner. In particular, layer formation is performedthrough solidification of photo curable resin under the action ofvisible or UV light irradiation. Two techniques are known: one in whichnew layers are formed at the top surface of the growing object; theother in which new layers are formed at the bottom surface of thegrowing object.

If new layers are formed at the top surface of the growing object, thenafter each irradiation step the object under construction is loweredinto the resin “pool,” a new layer of resin is coated on top, and a newirradiation step takes place. An early example of such a technique isgiven in Hull, U.S. Pat. No. 5,236,637, at FIG. 3. A disadvantage ofsuch “top down” techniques is the need to submerge the growing object ina (potentially deep) pool of liquid resin and reconstitute a preciseoverlayer of liquid resin.

If new layers are formed at the bottom of the growing object, then aftereach irradiation step the object under construction must be separatedfrom the bottom plate in the fabrication well. An early example of sucha technique is given in Hull, U.S. Pat. No. 5,236,637, at FIG. 4. Whilesuch “bottom up” techniques hold the potential to eliminate the need fora deep well in which the object is submerged by instead lifting theobject out of a relatively shallow well or pool, a problem with such“bottom up” fabrication techniques, as commercially implemented, is thatextreme care must be taken, and additional mechanical elements employed,when separating the solidified layer from the bottom plate due tophysical and chemical interactions therebetween. For example, in U.S.Pat. No. 7,438,846, an elastic separation layer is used to achieve“non-destructive” separation of solidified material at the bottomconstruction plane. Other approaches, such as the B9Creator™3-dimensional printer marketed by B9Creations of Deadwood, S. Dak., USA,employ a sliding build plate. See, e.g., M. Joyce, US Patent App.2013/0292862 and Y. Chen et al., US Patent App. 2013/0295212 (both Nov.7, 2013); see also Y. Pan et al., J. Manufacturing Sci. and Eng. 134,051011-1 (October 2012). Such approaches introduce a mechanical stepthat may complicate the apparatus, slow the method, and/or potentiallydistort the end product.

Continuous processes for producing a three-dimensional object aresuggested at some length with respect to “top down” techniques in U.S.Pat. No. 7,892,474, but this reference does not explain how they may beimplemented in “bottom up” systems in a manner non-destructive to thearticle being produced. Accordingly, there is a need for alternatemethods and apparatus for three-dimensional fabrication that can obviatethe need for mechanical separation steps in “bottom-up” fabrication.

SUMMARY OF THE INVENTION

Described herein are methods, systems and apparatus (includingassociated control methods, systems and apparatus), for the productionof a three-dimensional object by additive manufacturing. In preferred(but not necessarily limiting) embodiments, the method is carried outcontinuously. In preferred (but not necessarily limiting) embodiments,the three-dimensional object is produced from a liquid interface. Hencethey are sometimes referred to, for convenience and not for purposes oflimitation, as continuous liquid interface (or interphase) production(or printing), that is, “CLIP” herein (the various phrasings being usedinterchangeably). A schematic representation of one embodiment thereofis given in FIG. 1 herein.

The present invention provides a method of forming a three-dimensionalobject, comprising:

providing a carrier and an optically transparent member having a buildsurface, said carrier and said build surface defining a build regiontherebetween;

filling said build region with a polymerizable liquid,

continuously or intermittently irradiating said build region with lightthrough said optically transparent member to form a solid polymer fromsaid polymerizable liquid, and

continuously or intermittently advancing (e.g., sequentially orconcurrently with said irradiating step) said carrier away from saidbuild surface to form said three-dimensional object from said solidpolymer.

In some embodiments, illumination is carried out sequentially, andpreferably at higher intensity (e.g., in “strobe” mode), as describedfurther below.

In some embodiments, fabrication is carried out in two or threesequential patterns, from a base zone, through an optional transitionzone, to a body zone, as described further below.

In some embodiments, the carrier is vertically reciprocated with respectto the build surface, to enhance or speed the refilling of the buildregion with the polymerizable liquid.

In some preferred embodiments of CLIP, the filling, irradiating, and/oradvancing steps are carried out while also concurrently: (i)continuously maintaining a dead zone of polymerizable liquid in contactwith said build surface, and (ii) continuously maintaining a gradient ofpolymerization zone (which, as discussed below, may also be described asan active surface on the bottom of the growing three dimensional object)between said dead zone and said solid polymer and in contact with eachthereof, said gradient of polymerization zone comprising saidpolymerizable liquid in partially cured form. Stated differently, insome preferred embodiments of CLIP, the three dimensional object, or atleast some contiguous portion thereof, is formed or produced in situ.“In situ” as used herein has its meaning in the field of chemicalengineering, and means “in place.” For example, where both the growingportion of the three-dimensional object and the build surface (typicallywith their intervening active surface or gradient of polymerization, anddead zone) are maintained in place during formation of at least aportion of the 3D object, or sufficiently in place to avoid theformation of fault lines or planes in the 3D object. For example, insome embodiments according to the invention, different portions of the3D object, which are contiguous with one another in the final 3D object,can both be formed sequentially from or within a gradient ofpolymerization or active surface. Furthermore, a first portion of the 3Dobject can remain in the gradient of polymerization or contacting theactive surface while a second portion, that is contiguous with the firstportion, is formed in the gradient of polymerization. Accordingly, the3D object can be remotely fabricated, grown or produced continuouslyfrom the gradient of polymerization or active surface (rather thanfabricated in discrete layers). The dead zone and gradient ofpolymerization zone/active surface may be maintained through some or allof the formation of the object being made, for example (and in someembodiments) for a time of at least 5, 10, 20, or 30 seconds, and insome embodiments for a time of at least 1 or 2 minutes.

Apparatus for carrying out the present invention generally comprises:

(a) a support;

(b) a carrier operatively associated with said support on which carriersaid three-dimensional object is formed;

(c) an optically transparent member having a build surface, with saidbuild surface and said carrier defining a build region therebetween;

(d) a liquid polymer supply operatively associated with said buildsurface and configured to supply liquid polymer into said build regionfor solidification or polymerization;

(e) a radiation source configured to irradiate said build region throughsaid optically transparent member to form a solid polymer from saidpolymerizable liquid;

(f) optionally at least one drive operatively associated with eithersaid transparent member or said carrier;

(g) a controller operatively associated with said carrier, and/oroptionally said at least one drive, and said radiation source foradvancing said carrier away from said build surface to form saidthree-dimensional object from said solid polymer,

with the controller preferably further configured to oscillate orreciprocate said carrier with respect to said build surface to enhanceor speed the refilling of said build region with said polymerizableliquid.

In the B9Creator™ 3-dimensional printer, a polydimethylsiloxane (PDMS)coating is applied to the sliding build surface. The PDMS coating issaid to absorb oxygen and create a thin lubricating film ofunpolymerized resin through its action as a polymerization inhibitor.However, the PDMS coated build surface is directly replenished withoxygen by mechanically moving (sliding) the surface from beneath thegrowing object, while wiping unpolymerized resin therefrom with a wiperblade, and then returning it to its previous position beneath thegrowing object. While in some embodiments auxiliary means of providingan inhibitor such as oxygen are provided (e.g., a compressor toassociated channels), the process still employs a layer-by-layerapproach with sliding and wiping of the surface. Since the PDMS coatingmay be swollen by the resin, this swelling, along with these mechanicalsteps, may result in tearing of or damage to the PDMS coating.

Non-limiting examples and specific embodiments of the present inventionare explained in greater detail in the drawings herein and thespecification set forth below. The disclosure of all United StatesPatent references cited herein are to be incorporated herein byreference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of a method of thepresent invention.

FIG. 2 is a perspective view of one embodiment of an apparatus of thepresent invention.

FIGS. 3 to 5 are flow charts illustrating control systems and methodsfor carrying out the present invention.

FIG. 6 is a top view of a 3 inch by 16 inch “high aspect” rectangularbuild plate (or “window”) assembly of the present invention, where thefilm dimensions are 3.5 inch by 17 inch.

FIG. 7 is an exploded view of the build plate of FIG. 6, showing thetension ring and tension ring spring plate.

FIG. 8 is a side sectional view of the build plates of FIGS. 6-9,showing how the tension member tensions and fixes or rigidifies thepolymer film.

FIG. 9 is a top view of a 2.88 inch diameter round build plate of theinvention, where the film dimension may be 4 inches in diameter.

FIG. 10 is an exploded view of the build plate of FIG. 8.

FIG. 11 shows various alternate embodiments of the build plates of FIGS.7-10.

FIG. 12 is a front perspective view of an apparatus according to anexemplary embodiment of the invention.

FIG. 13 is a side view of the apparatus of FIG. 12.

FIG. 14 is a rear perspective view of the apparatus of FIG. 12.

FIG. 15 is a perspective view of a light engine assembly used with theapparatus of FIG. 12.

FIG. 16 is a front perspective view of an apparatus according to anotherexemplary embodiment of the invention.

FIGS. 17A-17C are schematic diagrams illustrating tiled images.

FIG. 18 is a front perspective view of an apparatus according to anotherexemplary embodiment of the invention.

FIG. 19 is a side view of the apparatus of FIG. 18.

FIG. 20 is a perspective view of a light engine assembly used with theapparatus of FIG. 18.

FIG. 21 is a graphic illustration of a process of the inventionindicating the position of the carrier in relation to the build surfaceor plate, where both advancing of the carrier and irradiation of thebuild region is carried out continuously. Advancing of the carrier isillustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 22 is a graphic illustration of another process of the inventionindicating the position of the carrier in relation to the build surfaceor plate, where both advancing of the carrier and irradiation of thebuild region is carried out stepwise, yet the dead zone and gradient ofpolymerization are maintained. Advancing of the carrier is againillustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 23 is a graphic illustration of still another process of theinvention indicating the position of the carrier in relation to thebuild surface or plate, where both advancing of the carrier andirradiation of the build region is carried out stepwise, the dead zoneand gradient of polymerization are maintained, and a reciprocating stepis introduced between irradiation steps to enhance the flow ofpolymerizable liquid into the build region. Advancing of the carrier isagain illustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 24 is a detailed illustration of a reciprocation step of FIG. 23,showing a period of acceleration occurring during the upstroke (i.e., agradual start of the upstroke) and a period of deceleration occurringduring the downstroke (i.e., a gradual end to the downstroke).

FIG. 25 schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byprocesses of the present invention through a first base (or “adhesion”)zone, a second transition zone, and a third body zone.

FIG. 26A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object bycontinuous advancing and continuous exposure.

FIG. 26B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 26 A, except that illumination is now in anintermittent (or “strobe”) pattern.

FIG. 27A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byintermittent (or “stepped”) advancing and intermittent exposure.

FIG. 27B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 27A, except that illumination is now in ashortened intermittent (or “strobe”) pattern.

FIG. 28A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byoscillatory advancing and intermittent exposure.

FIG. 28B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 28A, except that illumination is now in ashortened intermittent (or “strobe”) pattern.

FIG. 29A schematically illustrates one segment of a “strobe” pattern offabrication, where the duration of the static portion of the carrier hasbeen shortened to near the duration of the “strobe” exposure

FIG. 29B is a schematic illustration of a segment of a strobe pattern offabrication similar to FIG. 29A, except that the carrier is now movingslowly upward during the period of strobe illumination.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity. Where used, broken lines illustrate optionalfeatures or operations unless specified otherwise.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises” or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements components and/orgroups or combinations thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups or combinations thereof.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being “on,”“attached” to, “connected” to, “coupled” with, “contacting,” etc.,another element, it can be directly on, attached to, connected to,coupled with and/or contacting the other element or intervening elementscan also be present. In contrast, when an element is referred to asbeing, for example, “directly on,” “directly attached” to, “directlyconnected” to, “directly coupled” with or “directly contacting” anotherelement, there are no intervening elements present. It will also beappreciated by those of skill in the art that references to a structureor feature that is disposed “adjacent” another feature can have portionsthat overlap or underlie the adjacent feature.

Spatially relative terms, such as “under,” “below,” “lower,” “over,”“upper” and the like, may be used herein for ease of description todescribe an element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus the exemplary term “under” can encompass both anorientation of over and under. The device may otherwise be oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly,” “downwardly,” “vertical,” “horizontal” and the like are usedherein for the purpose of explanation only, unless specificallyindicated otherwise.

It will be understood that, although the terms first, second, etc., maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. Rather, these terms areonly used to distinguish one element, component, region, layer and/orsection, from another element, component, region, layer and/or section.Thus, a first element, component, region, layer or section discussedherein could be termed a second element, component, region, layer orsection without departing from the teachings of the present invention.The sequence of operations (or steps) is not limited to the orderpresented in the claims or figures unless specifically indicatedotherwise.

1. Polymerizable Liquids.

Any suitable polymerizable liquid can be used to enable the presentinvention. The liquid (sometimes also referred to as “liquid resin”“ink,” or simply “resin” herein) can include a monomer, particularlyphotopolymerizable and/or free radical polymerizable monomers, and asuitable initiator such as a free radical initiator, and combinationsthereof. Examples include, but are not limited to, acrylics,methacrylics, acrylamides, styrenics, olefins, halogenated olefins,cyclic alkenes, maleic anhydride, alkenes, alkynes, carbon monoxide,functionalized oligomers, multifunctional cure site monomers,functionalized PEGs, etc., including combinations thereof. Examples ofliquid resins, monomers and initiators include but are not limited tothose set forth in U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476;7,767,728; 7,649,029; WO 2012129968 A1; CN 102715751 A; JP 2012210408 A.

Acid Catalyzed Polymnerzable Liquids.

While in some embodiments as noted above the polymerizable liquidcomprises a free radical polymerizable liquid (in which case aninhibitor may be oxygen as described below), in other embodiments thepolymerizable liquid comprises an acid catalyzed, or cationicallypolymerized, polymerizable liquid. In such embodiments the polymerizableliquid comprises monomers contain groups suitable for acid catalysis,such as epoxide groups, vinyl ether groups, etc. Thus suitable monomersinclude olefins such as methoxyethene, 4-methoxystyrene, styrene,2-methylprop-1-ene, 1,3-butadiene, etc.; heterocycloic monomers(including lactones, lactams, and cyclic amines) such as oxirane,thietane, tetrahydrofuran, oxazoline, 1,3, dioxepane, oxetan-2-one,etc., and combinations thereof. A suitable (generally ionic ornon-ionic) photoacid generator (PAG) is included in the acid catalyzedpolymerizable liquid, examples of which include, but are not limited toonium salts, sulfonium and iodonium salts, etc., such as diphenyl iodidehexafluorophosphate, diphenyl iodide hexafluoroarsenate, diphenyl iodidehexafluoroantimonate, diphenyl p-methoxyphenyl triflate, diphenylp-toluenyl triflate, diphenyl p-isobutylphenyl triflate, diphenylp-tert-butylphenyl triflate, triphenylsulfonium hexafluororphosphate,triphenylsulfonium hexafluoroarsenate, triphenylsulfoniumhexafluoroantimonate, triphenylsulfonium triflate,dibutylnaphthylsulfonium triflate, etc., including mixtures thereof.See, e.g., U.S. Pat. Nos. 7,824,839; 7,550,246; 7,534,844; 6,692,891;5,374,500; and 5,017,461; see also Photoacid Generator Selection Guidefor the electronics industry and energy curable coatings (BASF 2010).

Hydrogels.

In some embodiments suitable resins includes photocurable hydrogels likepoly(ethylene glycols) (PEG) and gelatins. PEG hydrogels have been usedto deliver a variety of biologicals, including Growth factors; however,a great challenge facing PEG hydrogels crosslinked by chain growthpolymerizations is the potential for irreversible protein damage.Conditions to maximize release of the biologicals from photopolymerizedPEG diacrylate hydrogels can be enhanced by inclusion of affinitybinding peptide sequences in the monomer resin solutions, prior tophotopolymerization allowing sustained delivery. Gelatin is a biopolymerfrequently used in food, cosmetic, pharmaceutical and photographicindustries. It is obtained by thermal denaturation or chemical andphysical degradation of collagen. There are three kinds of gelatin,including those found in animals, fish and humans. Gelatin from the skinof cold water fish is considered safe to use in pharmaceuticalapplications. UV or visible light can be used to crosslink appropriatelymodified gelatin. Methods for crosslinking gelatin include curederivatives from dyes such as Rose Bengal.

Photocurable Silicone Resins.

A suitable resin includes photocurable silicones. UV cure siliconerubber, such as Silopren™ UV Cure Silicone Rubber can be used as canLOCTITE™ Cure Silicone adhesives sealants. Applications include opticalinstruments, medical and surgical equipment, exterior lighting andenclosures, electrical connectors/sensors, fiber optics and gaskets.

Biodegradable Resins.

Biodegradable resins are particularly important for implantable devicesto deliver drugs or for temporary performance applications, likebiodegradable screws and stents (U.S. Pat. Nos. 7,919,162; 6,932,930).Biodegradable copolymers of lactic acid and glycolic acid (PLGA) can bedissolved in PEG dimethacrylate to yield a transparent resin suitablefor use. Polycaprolactone and PLGA oligomers can be functionalized withacrylic or methacrylic groups to allow them to be effective resins foruse.

Photocurable Polyurethanes.

A particularly useful resin is photocurable polyurethanes. Aphotopolymerizable polyurethane composition comprising (1) apolyurethane based on an aliphatic diisocyanate, poly(hexamethyleneisophthalate glycol) and, optionally, 1,4-butanediol; (2) apolyfunctional acrylic ester, (3) a photoinitiator, and (4) ananti-oxidant, can be formulated so that it provides a hard,abrasion-resistant, and stain-resistant material (U.S. Pat. No.4,337,130). Photocurable thermoplastic polyurethane elastomersincorporate photoreactive diacetylene diols as chain extenders.

High Performance Resins.

In some embodiments, high performance resins are used. Such highperformance resins may sometimes require the use of heating to meltand/or reduce the viscosity thereof, as noted above and discussedfurther below. Examples of such resins include, but are not limited to,resins for those materials sometimes referred to as liquid crystallinepolymers of esters, ester-imide, and ester-amide oligomers, as describedin U.S. Pat. Nos. 7,507,784; 6,939,940. Since such resins are sometimesemployed as high-temperature thermoset resins, in the present inventionthey further comprise a suitable photoinitiator such as benzophenone,anthraquinone, and fluorenone initiators (including derivativesthereof), to initiate cross-linking on irradiation, as discussed furtherbelow.

Additional Example Resins.

Particularly useful resins for dental applications include EnvisionTEC'sClear Guide, EnvisionTEC's E-Denstone Material. Particularly usefulresins for hearing aid industries include EnvisionTEC's e-Shell 300Series of resins. Particularly useful resins include EnvisionTEC'sHTM140IV High Temperature Mold Material for use directly with vulcanizedrubber in molding/casting applications. A particularly useful materialfor making tough and stiff parts includes EnvisionTEC's RC31 resin. Aparticularly useful resin for investment casting applications includesEnvisionTEC's Easy Cast EC500.

Additional Resin Ingredients.

The liquid resin or polymerizable material can have solid particlessuspended or dispersed therein. Any suitable solid particle can be used,depending upon the end product being fabricated. The particles can bemetallic, organic/polymeric, inorganic, or composites or mixturesthereof. The particles can be nonconductive, semi-conductive, orconductive (including metallic and non-metallic or polymer conductors);and the particles can be magnetic, ferromagnetic, paramagnetic, ornonmagnetic. The particles can be of any suitable shape, includingspherical, elliptical, cylindrical, etc. The particles can comprise anactive agent or detectable compound as described below, though these mayalso be provided dissolved solubilized in the liquid resin as alsodiscussed below. For example, magnetic or paramagnetic particles ornanoparticles can be employed. The resin or polymerizable material maycontain a dispersing agent, such as an ionic surfactant, a non-ionicsurfactant, a block copolymer, or the like.

The liquid resin can have additional ingredients solubilized therein,including pigments, dyes, active compounds or pharmaceutical compounds,detectable compounds (e.g., fluorescent, phosphorescent, radioactive),etc., again depending upon the particular purpose of the product beingfabricated. Examples of such additional ingredients include, but are notlimited to, proteins, peptides, nucleic acids (DNA, RNA) such as siRNA,sugars, small organic compounds (drugs and drug-like compounds), etc.,including combinations thereof.

Inhibitors of Polymerization.

Inhibitors or polymerization inhibitors for use in the present inventionmay be in the form of a liquid or a gas. In some embodiments, gasinhibitors are preferred. The specific inhibitor will depend upon themonomer being polymerized and the polymerization reaction. For freeradical polymerization monomers, the inhibitor can conveniently beoxygen, which can be provided in the form of a gas such as air, a gasenriched in oxygen (optionally but in some embodiments preferablycontaining additional inert gases to reduce combustibility thereof), orin some embodiments pure oxygen gas. In alternate embodiments, such aswhere the monomer is polymerized by photoacid generator initiator, theinhibitor can be a base such as ammonia, trace amines (e.g. methylamine, ethyl amine, di and trialkyl amines such as dimethyl amine,diethyl amine, trimethyl amine, triethyl amine, etc.), or carbondioxide, including mixtures or combinations thereof.

Polymerizable Liquids Carrying Live Cells.

In some embodiments, the polymerizable liquid may carry live cells as“particles” therein. Such polymerizable liquids are generally aqueous,and may be oxygenated, and may be considered as “emulsions” where thelive cells are the discrete phase. Suitable live cells may be plantcells (e.g., monocot, dicot), animal cells (e.g., mammalian, avian,amphibian, reptile cells), microbial cells (e.g., prokaryote, eukaryote,protozoal, etc.), etc. The cells may be of differentiated cells from orcorresponding to any type of tissue (e.g., blood, cartilage, bone,muscle, endocrine gland, exocrine gland, epithelial, endothelial, etc.),or may be undifferentiated cells such as stem cells or progenitor cells.In such embodiments the polymerizable liquid can be one that forms ahydrogel, including but not limited to those described in U.S. Pat. Nos.7,651,683; 7,651,682; 7,556,490; 6,602,975; 5,836,313; etc.

2. Apparatus.

A non-limiting embodiment of an apparatus of the invention is shown inFIG. 2. It comprises a radiation source 11 such as a digital lightprocessor (DLP) providing electromagnetic radiation 12 which thoughreflective mirror 13 illuminates a build chamber defined by wall 14 anda rigid build plate 15 forming the bottom of the build chamber, whichbuild chamber is filled with liquid resin 16. The bottom of the chamber15 is constructed of build plate comprising a semipermeable member asdiscussed further below. The top of the object under construction 17 isattached to a carrier 18. The carrier is driven in the verticaldirection by linear stage 19, although alternate structures can be usedas discussed below.

A liquid resin reservoir, tubing, pumps liquid level sensors and/orvalves can be included to replenish the pool of liquid resin in thebuild chamber (not shown for clarity) though in some embodiments asimple gravity feed may be employed. Drives/actuators for the carrier orlinear stage, along with associated wiring, can be included inaccordance with known techniques (again not shown for clarity). Thedrives/actuators, radiation source, and in some embodiments pumps andliquid level sensors can all be operatively associated with a suitablecontroller, again in accordance with known techniques.

Build plates 15 used to carry out the present invention generallycomprise or consist of a (typically rigid or solid, stationary, and/orfixed, but may also be flexible) semipermeable (or gas permeable)member, alone or in combination with one or more additional supportingsubstrates (e.g., clamps and tensioning members to rigidify an otherwiseflexible semipermeable material). The semipermeable member can be madeof any suitable material that is optically transparent at the relevantwavelengths (or otherwise transparent to the radiation source, whetheror not it is visually transparent as perceived by the human eye—i.e., anoptically transparent window may in some embodiments be visuallyopaque), including but not limited to porous or microporous glass, andthe rigid gas permeable polymers used for the manufacture of rigid gaspermeable contact lenses. See, e.g., Norman G. Gaylord, U.S. Pat. No.RE31,406; see also U.S. Pat. Nos. 7,862,176; 7,344,731; 7,097,302;5,349,394; 5,310,571; 5,162,469; 5,141,665; 5,070,170; 4,923,906; and4,845,089. Other suitable oxygen-permeable materials may be used,including polyester, e.g., Mylar® from Dupont Tejjin Films, Chester,V.A., polyurethane, polyethelene, polychlorophene, mercapto ester-basedresins, e.g., Norland 60, from Norland Optical Products, Inc., NewBrunswich, N.J., porous Tygon® tubing from Saint-Gobain PerformancePlastics, Mickleton, N.J., or other materials. Still other Exemplaryoxygen-permeable materials are described in U.S. Pat. No. 7,709,544, thedisclosure of which is incorporated herein by reference.

In some embodiments, suitable oxygen-permeable materials arecharacterized as glassy and/or amorphous polymers and/or substantiallycrosslinked that they are essentially non-swellable. Preferably thesemipermeable member is formed of a material that does not swell whencontacted to the liquid resin or material to be polymerized (i.e., is“non-swellable”). Suitable materials for the semipermeable memberinclude amorphous fluoropolymers, such as those described in U.S. Pat.Nos. 5,308,685 and 5,051,115. For example, such fluoropolymers areparticularly useful over silicones that would potentially swell whenused in conjunction with organic liquid resin inks to be polymerized.For some liquid resin inks, such as more aqueous-based monomeric systemsand/or some polymeric resin ink systems that have low swellingtendencies, silicone based window materials maybe suitable. Thesolubility or permeability of organic liquid resin inks can bedramatically decreased by a number of known parameters includingincreasing the crosslink density of the window material or increasingthe molecular weight of the liquid resin ink. In some embodiments thebuild plate may be formed from a thin film or sheet of material which isflexible when separated from the apparatus of the invention, but whichis clamped and tensioned when installed in the apparatus (e.g., with atensioning ring) so that it is rendered fixed or rigid in the apparatus.Particular materials include TEFLON AF® fluoropolymers, commerciallyavailable from DuPont. Additional materials include perfluoropolyetherpolymers such as described in U.S. Pat. Nos. 8,268,446; 8,263,129;8,158,728; and 7,435,495.

It will be appreciated that essentially all solid materials, and most ofthose described above, have some inherent “flex” even though they may beconsidered “rigid,” depending on factors such as the shape and thicknessthereof and environmental factors such as the pressure and temperatureto which they are subjected. In addition, the terms “stationary” or“fixed” with respect to the build plate is intended to mean that nomechanical interruption of the process occurs, or no mechanism orstructure for mechanical interruption of the process (as in alayer-by-layer method or apparatus) is provided, even if a mechanism forincremental adjustment of the build plate (for example, adjustment thatdoes not lead to or cause collapse of the gradient of polymerizationzone) is provided), or if the build surface contributes to reciprocationto aid feeding of the polymerizable liquid, as described further below.

The semipermeable member typically comprises a top surface portion, abottom surface portion, and an edge surface portion. The build surfaceis on the top surface portion; and the feed surface may be on one, two,or all three of the top surface portion, the bottom surface portion,and/or the edge surface portion. In the embodiment illustrated in FIG. 2the feed surface is on the bottom surface portion, but alternateconfigurations where the feed surface is provided on an edge, and/or onthe top surface portion (close to but separate or spaced away from thebuild surface) can be implemented with routine skill.

The semipermeable member has, in some embodiments, a thickness of from0.01, 0.1 or 1 millimeters to 10 or 100 millimeters, or more (dependingupon the size of the item being fabricated, whether or not it islaminated to or in contact with an additional supporting plate such asglass, etc., as discussed further below.

The permeability of the semipermeable member to the polymerizationinhibitor will depend upon conditions such as the pressure of theatmosphere and/or inhibitor, the choice of inhibitor, the rate or speedof fabrication, etc. In general, when the inhibitor is oxygen, thepermeability of the semipermeable member to oxygen may be from 10 or 20Barrers, up to 1000 or 2000 Barrers, or more. For example, asemipermeable member with a permeability of 10 Barrers used with a pureoxygen, or highly enriched oxygen, atmosphere under a pressure of 150PSI may perform substantially the same as a semipermeable member with apermeability of 500 Barrers when the oxygen is supplied from the ambientatmosphere under atmospheric conditions.

Thus, the semipermeable member may comprise a flexible polymer film(having any suitable thickness, e.g., from 0.001, 0.01, 0.05, 0.1 or 1millimeters to 1, 5, 10, or 100 millimeters, or more), and the buildplate may further comprise a tensioning member (e.g., a peripheral clampand an operatively associated strain member or stretching member, as ina “drum head”; a plurality of peripheral clamps, etc., includingcombinations thereof) connected to the polymer film and to fix andrigidify the film (e.g., at least sufficiently so that the film does notstick to the object as the object is advanced and resiliently orelastically rebound therefrom). The film has a top surface and a bottomsurface, with the build surface on the top surface and the feed surfacepreferably on the bottom surface. In other embodiments, thesemipermeable member comprises: (i) a polymer film layer (having anysuitable thickness, e.g., from 0.001, 0.01, 0.1 or 1 millimeters to 5,10 or 100 millimeters, or more), having a top surface positioned forcontacting said polymerizable liquid and a bottom surface, and (ii) arigid, gas permeable, optically transparent supporting member (havingany suitable thickness, e.g., from 0.01, 0.1 or 1 millimeters to 10,100, or 200 millimeters, or more), contacting said film layer bottomsurface. The supporting member has a top surface contacting the filmlayer bottom surface, and the supporting member has a bottom surfacewhich may serve as the feed surface for the polymerization inhibitor.Any suitable materials that permit the polymerization inhibitor to passto the build surface may be used, including materials that aresemipermeable (that is, permeable to the polymerization inhibitor). Forexample, the polymer film or polymer film layer may, for example, be afluoropolymer film, such as an amorphous thermoplastic fluoropolymerlike TEFLON AF 1600™ or TEFLON AF 2400™ fluoropolymer films, orperfluoropolyether (PFPE), particularly a crosslinked PFPE film, or acrosslinked silicone polymer film. The supporting member comprises asilicone or crosslinked silicone polymer member such as apolydmiethylxiloxane member, a rigid gas permeable polymer member, orglass member, including porous or microporous glass. Films can belaminated or clamped directly to the rigid supporting member withoutadhesive (e.g., using PFPE and PDMS materials), or silane couplingagents that react with the upper surface of a PDMS layer can be utilizedto adhere to the first polymer film layer. UV-curable,acrylate-functional silicones can also be used as a tie layer betweenUV-curable PFPEs and rigid PDMS supporting layers.

When configured for placement in the apparatus, the carrier defines a“build region” on the build surface, within the total area of the buildsurface. Because lateral “throw” (e.g., in the X and/or Y directions) isnot required in the present invention to break adhesion betweensuccessive layers, as in the Joyce and Chen devices noted previously,the area of the build region within the build surface may be maximized(or conversely, the area of the build surface not devoted to the buildregion may be minimized). Hence in some embodiments, the total surfacearea of the build region can occupy at least fifty, sixty, seventy,eighty, or ninety percent of the total surface area of the buildsurface.

As shown in FIG. 2, the various components are mounted on a support orframe assembly 20. While the particular design of the support or frameassembly is not critical and can assume numerous configurations, in theillustrated embodiment it is comprised of a base 21 to which theradiation source 11 is securely or rigidly attached, a vertical member22 to which the linear stage is operatively associated, and a horizontaltable 23 to which wall 14 is removably or securely attached (or on whichthe wall is placed), and with the build plate rigidly fixed, eitherpermanently or removably, to form the build chamber as described above.

As noted above, the build plate can consist of a single unitary andintegral piece of a rigid semipermeable member, or can compriseadditional materials. For example, glass can be laminated or fixed to arigid semipermeable material. Or, a semipermeable member as an upperportion can be fixed to a transparent lower member having purgingchannels formed therein for feeding gas carrying the polymerizationinhibitor to the semipermeable member (through which it passes to thebuild surface to facilitate the formation of a release layer ofunpolymerized liquid material, as noted above and below). Such purgechannels may extend fully or partially through the base plate: Forexample, the purge channels may extend partially into the base plate,but then end in the region directly underlying the build surface toavoid introduction of distortion. Specific geometries will depend uponwhether the feed surface for the inhibitor into the semipermeable memberis located on the same side or opposite side as the build surface, on anedge portion thereof, or a combination of several thereof.

Any suitable radiation source (or combination of sources) can be used,depending upon the particular resin employed, including electron beamand ionizing radiation sources. In a preferred embodiment the radiationsource is an actinic radiation source, such as one or more lightsources, and in particular one or more ultraviolet light sources. Anysuitable light source can be used, such as incandescent lights,fluorescent lights, phosphorescent or luminescent lights, a laser,light-emitting diode, etc., including arrays thereof. The light sourcepreferably includes a pattern-forming element operatively associatedwith a controller, as noted above. In some embodiments, the light sourceor pattern forming element comprises a digital (or deformable)micromirror device (DMD) with digital light processing (DLP), a spatialmodulator (SLM), or a microelectromechanical system (MEMS) mirror array,a mask (aka a reticle), a silhouette, or a combination thereof. See,U.S. Pat. No. 7,902,526. Preferably the light source comprises a spatiallight modulation array such as a liquid crystal light valve array ormicromirror array or DMD (e.g., with an operatively associated digitallight processor, typically in turn under the control of a suitablecontroller), configured to carry out exposure or irradiation of thepolymerizable liquid without a mask, e.g., by maskless photolithography.See, e.g., U.S. Pat. Nos. 6,312,134; 6,248,509; 6,238,852; and5,691,541.

In some embodiments, as discussed further below, there may be movementin the X and/or Y directions concurrently with movement in the Zdirection, with the movement in the X and/or Y direction hence occurringduring polymerization of the polymerizable liquid (this is in contrastto the movement described in Y. Chen et al., or M. Joyce, supra, whichis movement between prior and subsequent polymerization steps for thepurpose of replenishing polymerizable liquid). In the present inventionsuch movement may be carried out for purposes such as reducing “burn in”or fouling in a particular zone of the build surface.

Because an advantage of some embodiments of the present invention isthat the size of the build surface on the semipermeable member (i.e.,the build plate or window) may be reduced due to the absence of arequirement for extensive lateral “throw” as in the Joyce or Chendevices noted above, in the methods, systems and apparatus of thepresent invention lateral movement (including movement in the X and/or Ydirection or combination thereof) of the carrier and object (if suchlateral movement is present) is preferably not more than, or less than,80, 70, 60, 50, 40, 30, 20, or even 10 percent of the width (in thedirection of that lateral movement) of the build region.

While in some embodiments the carrier is mounted on an elevator toadvance up and away from a stationary build plate, on other embodimentsthe converse arrangement may be used: That is, the carrier may be fixedand the build plate lowered to thereby advance the carrier awaytherefrom. Numerous different mechanical configurations will be apparentto those skilled in the art to achieve the same result.

Depending on the choice of material from which the carrier isfabricated, and the choice of polymer or resin from which the article ismade, adhesion of the article to the carrier may sometimes beinsufficient to retain the article on the carrier through to completionof the finished article or “build.” For example, an aluminum carrier mayhave lower adhesion than a poly(vinyl chloride) (or “PVC”) carrier.Hence one solution is to employ a carrier comprising a PVC on thesurface to which the article being fabricated is polymerized. If thispromotes too great an adhesion to conveniently separate the finishedpart from the carrier, then any of a variety of techniques can be usedto further secure the article to a less adhesive carrier, including butnot limited to the application of adhesive tape such as “Greener MaskingTape for Basic Painting #2025 High adhesion” to further secure thearticle to the carrier during fabrication.

3. Controller and Process Control.

The methods and apparatus of the invention can include process steps andapparatus features to implement process control, including feedback andfeed-forward control, to, for example, enhance the speed and/orreliability of the method.

A controller for use in carrying out the present invention may beimplemented as hardware circuitry, software, or a combination thereof.In one embodiment, the controller is a general purpose computer thatruns software, operatively associated with monitors, drives, pumps, andother components through suitable interface hardware and/or software.Suitable software for the control of a three-dimensional printing orfabrication method and apparatus as described herein includes, but isnot limited to, the ReplicatorG open source 3d printing program,3DPrint™ controller software from 3D systems, Slic3r, Skeinforge,KISSlicer, Repetier-Host, PrintRun, Cura, etc., including combinationsthereof.

Process parameters to directly or indirectly monitor, continuously orintermittently, during the process (e.g., during one, some or all ofsaid filling, irradiating and advancing steps) include, but are notlimited to, irradiation intensity, temperature of carrier, polymerizableliquid in the build zone, temperature of growing product, temperature ofbuild plate, pressure, speed of advance, pressure, force (e.g., exertedon the build plate through the carrier and product being fabricated),strain (e.g., exerted on the carrier by the growing product beingfabricated), thickness of release layer, etc.

Known parameters that may be used in feedback and/or feed-forwardcontrol systems include, but are not limited to, expected consumption ofpolymerizable liquid (e.g., from the known geometry or volume of thearticle being fabricated), degradation temperature of the polymer beingformed from the polymerizable liquid, etc.

Process conditions to directly or indirectly control, continuously orstep-wise, in response to a monitored parameter, and/or known parameters(e.g., during any or all of the process steps noted above), include, butare not limited to, rate of supply of polymerizable liquid, temperature,pressure, rate or speed of advance of carrier, intensity of irradiation,duration of irradiation (e.g. for each “slice”), etc.

For example, the temperature of the polymerizable liquid in the buildzone, or the temperature of the build plate, can be monitored, directlyor indirectly with an appropriate thermocouple, non-contact temperaturesensor (e.g., an infrared temperature sensor), or other suitabletemperature sensor, to determine whether the temperature exceeds thedegradation temperature of the polymerized product. If so, a processparameter may be adjusted through a controller to reduce the temperaturein the build zone and/or of the build plate. Suitable process parametersfor such adjustment may include: decreasing temperature with a cooler,decreasing the rate of advance of the carrier, decreasing intensity ofthe irradiation, decreasing duration of radiation exposure, etc.

In addition, the intensity of the irradiation source (e.g., anultraviolet light source such as a mercury lamp) may be monitored with aphotodetector to detect a decrease of intensity from the irriadiationsource (e.g., through routine degredation thereof during use). Ifdetected, a process parameter may be adjusted through a controller toaccommodate the loss of intensity. Suitable process parameters for suchadjustment may include: increasing temperature with a heater, decreasingthe rate of advance of the carrier, increasing power to the lightsource, etc.

As another example, control of temperature and/or pressure to enhancefabrication time may be achieved with heaters and coolers (individually,or in combination with one another and separately responsive to acontroller), and/or with a pressure supply (e.g., pump, pressure vessel,valves and combinations thereof) and/or a pressure release mechanismsuch as a controllable valve (individually, or in combination with oneanother and separately responsive to a controller).

In some embodiments the controller is configured to maintain thegradient of polymerization zone described herein (see, e.g., FIG. 1)throughout the fabrication of some or all of the final product. Thespecific configuration (e.g., times, rate or speed of advancing,radiation intensity, temperature, etc.) will depend upon factors such asthe nature of the specific polymerizable liquid and the product beingcreated. Configuration to maintain the gradient of polymerization zonemay be carried out empirically, by entering a set of process parametersor instructions previously determined, or determined through a series oftest runs or “trial and error”; configuration may be provided throughpre-determined instructions; configuration may be achieved by suitablemonitoring and feedback (as discussed above), combinations thereof, orin any other suitable manner.

In some embodiments, a method and apparatus as described above may becontrolled by a software program running in a general purpose computerwith suitable interface hardware between that computer and the apparatusdescribed above. Numerous alternatives are commercially available.Non-limiting examples of one combination of components is shown in FIGS.3 to 5, where “Microcontroller” is Parallax Propeller, the Stepper MotorDriver is Sparkfun EasyDriver, the LED Driver is a Luxeon Single LEDDriver, the USB to Serial is a Parallax USB to Serial converter, and theDLP System is a Texas Instruments LightCrafter system.

4. General Methods.

As noted above, the present invention provides a method of forming athree-dimensional object, comprising the steps of: (a) providing acarrier and a build plate, said build plate comprising a semipermeablemember, said semipermeable member comprising a build surface and a feedsurface separate from said build surface, with said build surface andsaid carrier defining a build region therebetween, and with said feedsurface in fluid contact with a polymerization inhibitor, then(concurrently and/or sequentially) (b) filing said build region with apolymerizable liquid, said polymerizable liquid contacting said buildsegment, (c) irradiating said build region through said build plate toproduce a solid polymerized region in said build region, with a liquidfilm release layer comprised of said polymerizable liquid formed betweensaid solid polymerized region and said build surface, the polymerizationof which liquid film is inhibited by said polymerization inhibitor; and(d) advancing said carrier with said polymerized region adhered theretoaway from said build surface on said stationary build plate to create asubsequent build region between said polymerized region and said topzone. In general the method includes (e) continuing and/or repeatingsteps (b) through (d) to produce a subsequent polymerized region adheredto a previous polymerized region until the continued or repeateddeposition of polymerized regions adhered to one another forms saidthree-dimensional object.

Since no mechanical release of a release layer is required, or nomechanical movement of a build surface to replenish oxygen is required,the method can be carried out in a continuous fashion, though it will beappreciated that the individual steps noted above may be carried outsequentially, concurrently, or a combination thereof. Indeed, the rateof steps can be varied over time depending upon factors such as thedensity and/or complexity of the region under fabrication.

Also, since mechanical release from a window or from a release layergenerally requires that the carrier be advanced a greater distance fromthe build plate than desired for the next irradiation step, whichenables the window to be recoated, and then return of the carrier backcloser to the build plate (e.g., a “two steps forward one step back”operation), the present invention in some embodiments permitselimination of this “back-up” step and allows the carrier to be advancedunidirectionally, or in a single direction, without intervening movementof the window for re-coating, or “snapping” of a pre-formed elasticrelease-layer. However, in other embodiments of the invention,reciprocation is utilized not for the purpose of obtaining release, butfor the purpose of more rapidly filling or pumping polymerizable liquidinto the build region.

In some embodiments, the advancing step is carried out sequentially inuniform increments (e.g., of from 0.1 or 1 microns, up to 10 or 100microns, or more) for each step or increment. In some embodiments, theadvancing step is carried out sequentially in variable increments (e.g.,each increment ranging from 0.1 or 1 microns, up to 10 or 100 microns,or more) for each step or increment. The size of the increment, alongwith the rate of advancing, will depend in part upon factors such astemperature, pressure, structure of the article being produced (e.g.,size, density, complexity, configuration, etc.)

In other embodiments of the invention, the advancing step is carried outcontinuously, at a uniform or variable rate.

In some embodiments, the rate of advance (whether carried outsequentially or continuously) is from about 0.1 1, or 10 microns persecond, up to about to 100, 1,000, or 10,000 microns per second, againdepending again depending on factors such as temperature, pressure,structure of the article being produced, intensity of radiation, etc Asdescribed further below, in some embodiments the filling step is carriedout by forcing said polymerizable liquid into said build region underpressure. In such a case, the advancing step or steps may be carried outat a rate or cumulative or average rate of at least 0.1, 1, 10, 50, 100,500 or 1000 microns per second, or more. In general, the pressure may bewhatever is sufficient to increase the rate of said advancing step(s) atleast 2, 4, 6, 8 or 10 times as compared to the maximum rate ofrepetition of said advancing steps in the absence of said pressure.Where the pressure is provided by enclosing an apparatus such asdescribed above in a pressure vessel and carrying the process out in apressurized atmosphere (e.g., of air, air enriched with oxygen, a blendof gasses, pure oxygen, etc.) a pressure of 10, 20, 30 or 40 pounds persquare inch (PSI) up to, 200, 300, 400 or 500 PSI or more, may be used.For fabrication of large irregular objects higher pressures may be lesspreferred as compared to slower fabrication times due to the cost of alarge high pressure vessel. In such an embodiment, both the feed surfaceand the polymerizable liquid can be in fluid contact with the samecompressed gas (e.g., one comprising from 20 to 95 percent by volume ofoxygen, the oxygen serving as the polymerization inhibitor.

On the other hand, when smaller items are fabricated, or a rod or fiberis fabricated that can be removed or exited from the pressure vessel asit is produced through a port or orifice therein, then the size of thepressure vessel can be kept smaller relative to the size of the productbeing fabricated and higher pressures can (if desired) be more readilyutilized.

As noted above, the irradiating step is in some embodiments carried outwith patterned irradiation. The patterned irradiation may be a fixedpattern or may be a variable pattern created by a pattern generator(e.g., a DLP) as discussed above, depending upon the particular itembeing fabricated.

When the patterned irradiation is a variable pattern rather than apattern that is held constant over time, then each irradiating step maybe any suitable time or duration depending on factors such as theintensity of the irradiation, the presence or absence of dyes in thepolymerizable material, the rate of growth, etc. Thus in someembodiments each irradiating step can be from 0.001, 0.01, 0.1, 1 or 10microseconds, up to 1, 10, or 100 minutes, or more, in duration. Theinterval between each irradiating step is in some embodiments preferablyas brief as possible, e.g., from 0.001, 0.01, 0.1, or 1 microseconds upto 0.1, 1, or 10 seconds.

While the dead zone and the gradient of polymerization zone do not havea strict boundary therebetween (in those locations where the two meet),the thickness of the gradient of polymerization zone is in someembodiments at least as great as the thickness of the dead zone. Thus,in some embodiments, the dead zone has a thickness of from 0.01, 0.1, 1,2, or 10 microns up to 100, 200 or 400 microns, or more, and/or saidgradient of polymerization zone and said dead zone together have athickness of from 1 or 2 microns up to 400, 600, or 1000 microns, ormore. Thus the gradient of polymerization zone may be thick or thindepending on the particular process conditions at that time. Where thegradient of polymerization zone is thin, it may also be described as anactive surface on the bottom of the growing three-dimensional object,with which monomers can react and continue to form growing polymerchains therewith. In some embodiments, the gradient of polymerizationzone, or active surface, is maintained (while polymerizing stepscontinue) for a time of at least 5, 10, 15, 20 or 30 seconds, up to 5,10, 15 or 20 minutes or more, or until completion of thethree-dimensional product.

The method may further comprise the step of disrupting said gradient ofpolymerization zone for a time sufficient to form a cleavage line insaid three-dimensional object (e.g., at a predetermined desired locationfor intentional cleavage, or at a location in said object whereprevention of cleavage or reduction of cleavage is non-critical), andthen reinstating said gradient of polymerization zone (e.g. by pausing,and resuming, the advancing step, increasing, then decreasing, theintensity of irradiation, and combinations thereof

In some embodiments the build surface is flat; in other the buildsurface is irregular such as convexly or concavely curved, or has wallsor trenches formed therein. In either case the build surface may besmooth or textured.

Curved and/or irregular build plates or build surfaces can be used infiber or rod formation, to provide different materials to a singleobject being fabricated (that is, different polymerizable liquids to thesame build surface through channels or trenches formed in the buildsurface, each associated with a separate liquid supply, etc.

Carrier Feed Channels for Polymerizable Liquid.

While polymerizable liquid may be provided directly to the build platefrom a liquid conduit and reservoir system, in some embodiments thecarrier include one or more feed channels therein. The carrier feedchannels are in fluid communication with the polymerizable liquidsupply, for example a reservoir and associated pump. Different carrierfeed channels may be in fluid communication with the same supply andoperate simultaneously with one another, or different carrier feedchannels may be separately controllable from one another (for example,through the provision of a pump and/or valve for each). Separatelycontrollable feed channels may be in fluid communication with areservoir containing the same polymerizable liquid, or may be in fluidcommunication with a reservoir containing different polymerizableliquids. Through the use of valve assemblies, different polymerizableliquids may in some embodiments be alternately fed through the same feedchannel, if desired.

5. Reciprocating Feed of Polymerizable Liquid.

In an embodiment of the present invention, the carrier is verticallyreciprocated with respect to the build surface (that is, the two arevertically reciprocated with respect to one another) to enhance or speedthe refilling of the build region with the polymerizable liquid.

In some embodiments, the vertically reciprocating step, which comprisesan upstroke and a downstroke, is carried out with the distance of travelof the upstroke being greater than the distance of travel of thedownstroke, to thereby concurrently carry out the advancing step (thatis, driving the carrier away from the build plate in the Z dimension) inpart or in whole.

In some embodiments, the speed of the upstroke gradually accelerates(that is, there is provided a gradual start and/or gradual accelerationof the upstroke, over a period of at least 20, 30, 40, or 50 percent ofthe total time of the upstroke, until the conclusion of the upstroke, orthe change of direction which represents the beginning of thedownstroke. Stated differently, the upstroke begins, or starts, gentlyor gradually.

In some embodiments, the speed of the downstroke gradually decelerates(that is, there is provided a gradual termination and/or gradualdeceleration of the downstroke, over a period of at least 20, 30, 40, or50 percent of the total time of the downstroke. Stated differently, thedownstroke concludes, or ends, gently or gradually.

While in some embodiments there is an abrupt end, or abruptdeceleration, of the upstroke, and an abrupt beginning or decelerationof the downstroke (e.g., a rapid change in vector or direction of travelfrom upstroke to downstroke), it will be appreciated that gradualtransitions may be introduced here as well (e.g., through introductionof a “plateau” or pause in travel between the upstroke and downstroke).It will also be appreciated that, while each reciprocating step may beconsist of a single upstroke and downstroke, the reciprocation step maycomprise a plurality of 2, 3, 4 or 5 or more linked set ofreciprocations, which may e the same or different in frequent and/oramplitude

In some embodiments, the vertically reciprocating step is carried outover a total time of from 0.01 or 0.1 seconds up to 1 or 10 seconds(e.g., per cycle of an upstroke and a downstroke).

In some embodiments, the upstroke distance of travel is from 0.02 or 0.2millimeters (or 20 or 200 microns) to 1 or 10 millimeters (or 1000 to10,000 microns). The distance of travel of the downstroke may be thesame as, or less than, the distance of travel of the upstroke, where alesser distance of travel for the downstroke serves to achieve theadvancing of the carrier away from the build surface as thethree-dimensional object is gradually formed. Where a reciprocation stepcomprises multiple linked reciprocations, the sum distance of travel ofall upstrokes in that set is preferably greater than the sum distance oftravel of all downstrokes in that set, to achieve the advancing of thecarrier away from the build surface as the three-dimensional object isgradually formed.

Preferably the vertically reciprocating step, and particularly theupstroke thereof, does not cause the formation of gas bubbles or a gaspocket in the build region, but instead the build region remains filledwith the polymerizable liquid throughout the reciprocation steps, andthe gradient of polymerization zone or region remains in contact withthe “dead zone” and with the growing object being fabricated throughoutthe reciprocation steps. As will be appreciated, a purpose of thereciprocation is to speed or enhance the refilling of the build region,particularly where larger build regions are to be refilled withpolymerizable liquid, as compared to the speed at which the build regioncould be refilled without the reciprocation step.

In some embodiments, the advancing step is carried out intermittently ata rate of 1, 2, 5 or 10 individual advances per minute up to 300, 600,or 1000 individual advances per minute, each followed by a pause duringwhich an irradiating step is carried out. It will be appreciated thatone or more reciprocation steps (e.g., upstroke plus downstroke) may becarried out within each advancing step. Stated differently, thereciprocating steps may be nested within the advancing steps.

In some embodiments, the individual advances are carried out over anaverage distance of travel for each advance of from 10 or 50 microns to100 or 200 microns (optionally including the total distance of travelfor each vertically reciprocating step, e.g., the sum of the upstrokedistance minus the downstroke distance).

Apparatus for carrying out the invention in which the reciprocationsteps described herein are implemented substantially as described above,with the drive associated with the carrier, and/or with an additionaldrive operatively associated with the transparent member, and with thecontroller operatively associated with either or both thereof andconfigured to reciprocate the carrier and transparent member withrespect to one another as described above.

In the alternative, vertical reciprocation may be carried out byconfiguring the build surface (and corresponding build plate) so that itmay have a limited range of movement up and down in the vertical or “Z”dimension, while the carrier advances (e.g., continuously or step-wise)away from the build plate in the vertical or “Z” dimension. In someembodiments, such limited range of movement may be passively imparted,such as with upward motion achieved by partial adhesion of the buildplate to the growing object through a viscous polymerizable liquid,followed by downward motion achieved by the weight, resiliency, etc. ofthe build plate (optionally including springs, buffers, shock absorbersor the like, configured to influence either upward or downward motion ofthe build plate and build surface). In another embodiment, such motionof the build surface may be actively achieved, by operativelyassociating a separate drive system with the build plate, which drivesystem is also operatively associated with the controller, to separatelyachieve vertical reciprocation. In still another embodiment, verticalreciprocation may be carried out by configuring the build plate, and/orthe build surface, so that it flexes upward and downward, with theupward motion thereof being achieved by partial adhesion of the buildsurface to the growing object through a viscous polymerizable liquid,followed by downward motion achieved by the inherent stiffness of thebuild surface biasing it or causing it to return to a prior position.

It will be appreciated that illumination or irradiation steps, whenintermittent, may be carried out in a manner synchronized with verticalreciprocation, or not synchronized with vertical reciprocation,depending on factors such as whether the reciprocation is achievedactively or passively.

It will also be appreciated that vertical reciprocation may be carriedout between the carrier and all regions of the build surfacesimultaneously (e.g., where the build surface is rigid), or may becarried out between the carrier and different regions of the buildsurface at different times (e.g., where the build surface is of aflexible material, such as a tensioned polymer film).

6. Increased Speed of Fabrication by Increasing Light Intensity.

In general, it has been observed that speed of fabrication can increasewith increased light intensity. In some embodiments, the light isconcentrated or “focused” at the build region to increase the speed offabrication. This may be accomplished using an optical device such as anobjective lens.

The speed of fabrication may be generally proportional to the lightintensity. For example, the build speed in millimeters per hour may becalculated by multiplying the light intensity in milliWatts per squarecentimeter and a multiplier. The multiplier may depend on a variety offactors, including those discussed below. A range of multiplers, fromlow to high, may be employed. On the low end of the range, themultiplier may be about 10, 15, 20 or 30. On the high end of themultiplier range, the multiplier may be about 150, 300, 400 or more.

The relationships described above are, in general, contemplated forlight intensities of from 1, 5 or 10 milliWatts per square centimeter,up to 20 or 50 milliWatts per square centimeter.

Certain optical characteristics of the light may be selected tofacilitate increased speed of fabrication. By way of example, a bandpass filter may be used with a mercury bulb light source to provide365±10 nm light measured at Full Width Half Maximum (FWHM). By way offurther example, a band pass filter may be used with an LED light sourceto provide 375±15 nm light measured at FWHM.

As noted above, poymerizable liquids used in such processes are, ingeneral, free radical polymerizable liquids with oxygen as theinhibitor, or acid-catalyzed or cationically polymerizable liquids witha base as the inhibitor. Some specific polymerizable liquids will ofcourse cure more rapidly or efficiently than others and hence be moreamenable to higher speeds, though this may be offset at least in part byfurther increasing light intensity.

At higher light intensities and speeds, the “dead zone” may becomethinner as inhibitor is consumed. If the dead zone is lost then theprocess will be disrupted. In such case, the supply of inhibitor may beenhanced by any suitable means, including providing an enriched and/orpressurized atmosphere of inhibitor, a more porous semipermeable member,a stronger or more powerful inhibitor (particularly where a base isemployed), etc.

In general, lower viscosity polymerizable liquids are more amenable tohigher speeds, particularly for fabrication of articles with a largeand/or dense cross section (although this can be offset at least in partby increasing light intensity). Polymerizable liquids with viscositiesin the range of 50 or 100 centipoise, up to 600, 800 or 1000 centipoiseor more (as measured at room temperature and atmospheric pressure with asuitable device such as a HYDRAMOTION REACTAVISC™ Viscometer (availablefrom Hydramotion Ltd, 1 York Road Business Park, Malton, York YO17 6YAEngland). In some embodiments, where necessary, the viscosity of thepolymerizable liquid can advantageously be reduced by heating thepolymerizable liquid, as described above.

In some embodiments, such as fabrication of articles with a large and/ordense cross-section, speed of fabrication can be enhanced by introducingreciprocation to “pump” the polymerizable liquid, as described above,and/or the use of feeding the polymerizable liquid through the carrier,as also described above, and/or heating and/or pressurizing thepolymerizable liquid, as also described above.

7. Tiling.

It may be desirable to use more than one light engine to preserveresolution and light intensity for larger build sizes. Each light enginemay be configured to project an image (e.g., an array of pixels) intothe build region such that a plurality of “tiled” images are projectedinto the build region. As used herein, the term “light engine” can meanan assembly including a light source, a DLP device such as a digitalmicromirror device and an optical device such as an objective lens. The“light engine” may also include electronics such as a controller that isoperatively associated with one or more of the other components.

This is shown schematically in FIGS. 17A-17C. The light engineassemblies 130A, 130B produce adjacent or “tiled” images 140A, 140B. InFIG. 17A, the images are slightly misaligned; that is, there is a gapbetween them. In FIG. 17B, the images are aligned, there is no gap andno overlap between them. In FIG. 17C, there is a slight overlap of theimages 140A and 140B.

In some embodiments, the configuration with the overlapped images shownin FIG. 17C is employed with some form of “blending” or “smoothing” ofthe overlapped regions as generally discussed in, for example, U.S. Pat.Nos. 7,292,207, 8,102,332, 8,427,391, 8,446,431 and U.S. PatentApplication Publication Nos. 2013/0269882, 2013/0278840 and2013/0321475, the disclosures of which are incorporated herein in theirentireties. The tiled images can allow for larger build areas withoutsacrificing light intensity, and therefore can facilitate faster buildspeeds for larger objects. It will be understood that more than twolight engine assemblies (and corresponding tiled images) may beemployed. Various embodiments of the invention employ at least 4, 8, 16,32, 64, 128 or more tiled images.

8. Fabrication in Multiple Zones.

As noted above, embodiments of the invention may carry out the formationof the three-dimensional object through multiple zones or segments ofoperation. Such a method generally comprises:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween, with the carrier positioned adjacent and spaced apart fromthe build surface at a start position; then

(b) forming an adhesion segment of the three-dimensional object by:

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) irradiating the build region with light through the        optically transparent member (e.g., by a single exposure), while    -   (iii) maintaining the carrier stationary or advancing the        carrier away from the build surface at a first cumulative rate        of advance, to thereby form from the polymerizable liquid a        solid polymer adhesion segment of the object adhered to the        carrier, then

(c) optionally but preferably forming a transition segment of the threedimensional object by

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) continuously or intermittently irradiating the build region        with light through the optically transparent member, and    -   (iii) continuously or intermittently advancing (e.g.,        sequentially or concurrently with the irradiating step) the        carrier away from the build surface at a second cumulative rate        of advance to thereby form from the polymerizable liquid a        transition segment of the object between the adhesion segment        and the build surface;    -   wherein the second cumulative rate of advance is greater than        the first cumulative rate of advance; and then

(d) forming a body segment of the three dimensional object by:

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) continuously or intermittently irradiating the build region        with light through the optically transparent, and    -   (iii) continuously or intermittently advancing (e.g.,        sequentially or concurrently with the irradiating step) the        carrier away from the build surface at a third cumulative rate        of advance, to thereby form from the polymerizable liquid a body        segment of the object between the transition segment and the        build surface;

wherein the third cumulative rate of advance is greater than the firstand/or the second cumulative rate of advance.

Note that the start position can be any position among a range ofpositions (e.g., a range of up to 5 or 10 millimeters or more), and theirradiating step (b)(ii) is carried out at an intensity sufficient toadhere the solid polymer to the carrier when the carrier is at anyposition within that range of positions. This advantageously reduces thepossibility of failure of adhesion of the three-dimensional object tothe carrier due to variations in uniformity of the carrier and/or buildsurfaces, variations inherent in drive systems in positioning thecarrier adjacent the build surface, etc.

9. Fabrication with Intermittent (or Strobe”) Illumination.

As noted above, in some embodiments the invention may be carried outwith the illumination in intermittent periods or burst. In oneembodiment, such a method comprises:

providing a carrier and an optically transparent member having a buildsurface, the carrier and the build surface defining a build regiontherebetween;

filling the build region with a polymerizable liquid,

intermittently irradiating the build region with light through theoptically transparent member to form a solid polymer from thepolymerizable liquid,

continuously advancing the carrier away from the build surface to formthe three-dimensional object from the solid polymer.

Another embodiment of such a mode of operation comprises:

providing a carrier and an optically transparent member having a buildsurface, the carrier and the build surface defining a build regiontherebetween;

filling the build region with a polymerizable liquid,

intermittently irradiating the build region with light through theoptically transparent member to form a solid polymer from thepolymerizable liquid,

continuously or intermittently advancing (e.g., sequentially orconcurrently with the irradiating step) the carrier away from the buildsurface to form the three-dimensional object from the solid polymer.

In some embodiments, the intermittently irradiating comprisesalternating periods of active and inactive illumination, where theaverage duration of the periods of active illumination is less than theaverage duration of the periods of inactive illumination (e.g., is notmore than 50, 60, or 80 percent thereof).

In other embodiments, the intermittently irradiating comprisesalternating periods of active and inactive illumination, where theaverage duration of the periods of active illumination is the same as orgreater than the average duration of the periods of inactiveillumination (e.g., is at least 100, 120, 160, or 180 percent thereof).

Examples of such modes of operation are given further below. Thesefeatures may be combined with any of the other features and operatingsteps or parameters described herein.

10. Fabrication Products.

Three-dimensional products produced by the methods and processes of thepresent invention may be final, finished or substantially finishedproducts, or may be intermediate products subject to furthermanufacturing steps such as surface treatment, laser cutting, electricdischarge machining, etc., is intended. Intermediate products includeproducts for which further additive manufacturing, in the same or adifferent apparatus, may be carried out). For example, a fault orcleavage line may be introduced deliberately into an ongoing “build” bydisrupting, and then reinstating, the gradient of polymerization zone,to terminate one region of the finished product, or simply because aparticular region of the finished product or “build” is less fragilethan others.

Numerous different products can be made by the methods and apparatus ofthe present invention, including both large-scale models or prototypes,small custom products, miniature or microminiature products or devices,etc. Examples include, but are not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,functional structures, microneedle arrays, fibers and rods such aswaveguides, micromechanical devices, microfluidic devices, etc.

Thus in some embodiments the product can have a height of from 0.1 or 1millimeters up to 10 or 100 millimeters, or more, and/or a maximum widthof from 0.1 or 1 millimeters up to 10 or 100 millimeters, or more. Inother embodiments, the product can have a height of from 10 or 100nanometers up to 10 or 100 microns, or more, and/or a maximum width offrom 10 or 100 nanometers up to 10 or 100 microns, or more. These areexamples only: Maximum size and width depends on the architecture of theparticular device and the resolution of the light source and can beadjusted depending upon the particular goal of the embodiment or articlebeing fabricated.

In some embodiments, the ratio of height to width of the product is atleast 2:1, 10:1, 50:1, or 100:1, or more, or a width to height ratio of1:1, 10:1, 50:1, or 100:1, or more.

In some embodiments, the product has at least one, or a plurality of,pores or channels formed therein, as discussed further below.

The processes described herein can produce products with a variety ofdifferent properties. Hence in some embodiments the products are rigid;in other embodiments the products are flexible or resilient. In someembodiments, the products are a solid; in other embodiments, theproducts are a gel such as a hydrogel. In some embodiments, the productshave a shape memory (that is, return substantially to a previous shapeafter being deformed, so long as they are not deformed to the point ofstructural failure). In some embodiments, the products are unitary (thatis, formed of a single polymerizable liquid); in some embodiments, theproducts are composites (that is, formed of two or more differentpolymerizable liquids). Particular properties will be determined byfactors such as the choice of polymerizable liquid(s) employed.

In some embodiments, the product or article made has at least oneoverhanging feature (or “overhang”), such as a bridging element betweentwo supporting bodies, or a cantilevered element projecting from onesubstantially vertical support body. Because of the unidirectional,continuous nature of some embodiments of the present processes, theproblem of fault or cleavage lines that form between layers when eachlayer is polymerized to substantial completion and a substantial timeinterval occurs before the next pattern is exposed, is substantiallyreduced. Hence, in some embodiments the methods are particularlyadvantageous in reducing, or eliminating, the number of supportstructures for such overhangs that are fabricated concurrently with thearticle.

11. Alternate Methods and Apparatus.

While the present invention is preferably carried out by continuousliquid interphase polymerization, as described in detail above and infurther detail below, in some embodiments alternate methods andapparatus for bottom-up three-dimension fabrication may be used,including layer-by-layer fabrication. Examples of such methods andapparatus include, but are not limited to, those described in U.S. Pat.No. 5,236,637 to Hull, U.S. Pat. No. 7,438,846 to John and U.S. Pat. No.8,110,135 to El-Siblani, and in U.S. Patent Application Publication Nos.2013/0292862 to Joyce and 2013/0295212 to Chen et al. The disclosures ofthese patents and applications are incorporated by reference herein intheir entirety.

The present invention is explained in greater detail in the followingnon-limiting Examples, and features which may be incorporated incarrying out the present invention are further explained in PCTApplications Nos. PCT/US2014/015486 (also published as US 2015/0102532);PCT/US2014/015506 (also published as US 2015/0097315), PCT/US2014/015497(also published as US 2015/0097316), and in J. Tumbleston, D.Shirvanyants, N. Ermoshkin et al., Continuous liquid interfaceproduction of 3D Objects, Sciencexpress (16 Mar. 2015).

Example 1 High Aspect Ratio Adjustable Tension Build Plate Assembly

FIG. 6 is a top view and FIG. 7 is an exploded view of a 3 inch by 16inch “high aspect” rectangular build plate (or “window”) assembly of thepresent invention, where the film dimensions are 3.5 inches by 17inches. The greater size of the film itself as compared to the internaldiameter of vat ring and film base provides a peripheral orcircumferential flange portion in the film that is clamped between thevat ring and the film base, as shown in side-sectional view in FIG. 8.One or more registration holes (not shown) may be provided in thepolymer film in the peripheral or circumferential flange portion to aidin aligning the polymer film between the vat ring and film base, whichare fastened to one another with a plurality of screws (not shown)extending from one to the other (some or all passing through holes inthe peripheral edge of the polymer film) in a manner that rigidly andsecurely clamps the polymer film therebetween, while optionally allowingsome flexibility to contribute to embodiments employing verticalreciprocation, as noted above.

As shown in FIGS. 7-8 a tension ring is provided that abuts the polymerfilm and stretches the film to fix or rigidify the film. The tensionring may be provided as a pre-set member, or may be an adjustablemember. Adjustment may be achieved by providing a spring plate facingthe tension ring, with one or more compressible elements such as polymercushions or springs (e.g., flat springs, coil springs, wave springsetc.) therebetween, and with adjustable fasteners such as screwfasteners or the like passing from the spring plate through (or around)the tension ring to the film base.

Polymer films are preferably fluoropolymer films, such as an amorphousthermoplastic fluoropolymer, in a thickness of 0.01 or 0.05 millimetersto 0.1 or 1 millimeters, or more. In some embodiments we use BiogeneralTeflon AF 2400 polymer film, which is 0.0035 inches (0.09 millimeters)thick, and Random Technologies Teflon AF 2400 polymer film, which is0.004 inches (0.1 millimeters) thick.

Tension on the film is preferably adjusted with the tension ring toabout 10 to 100 pounds, depending on operating conditions such asfabrication speed.

The vat ring, film base, tension ring, and tension ring spring plate maybe fabricated of any suitable, preferably rigid, material, includingmetals (e.g., stainless steel, aluminum and aluminum alloys), carbonfiber, polymers, and composites thereof.

Registration posts and corresponding sockets may be provided in any ofthe vat ring, film base, tension ring and/or spring plate, as desired.

Example 2 Round Adjustable Tension Round Build Plate Assembly

FIG. 9 is a top view and FIG. 10 is an exploded view of a 2.88 inchdiameter round build plate of the invention, where the film dimensionmay be 4 inches in diameter. Construction is in like manner to thatgiven in Example 1 above, with a circumferential wave spring assemblyshown in place. Tension on the film preferably adjusted to a liketension as given in Example 1 above (again depending on other operatingconditions such as fabrication speed).

FIG. 10 is an exploded view of the build plate of FIG. 8.

Example 3 Additional Embodiments of Adjustable Build Plates

FIG. 11 shows various alternate embodiments of the build plates of FIGS.7-10. Materials and tensions may be in like manner as described above.

Example 4 Example Embodiment of an Apparatus

FIG. 12 is a front perspective view, FIG. 13 is a side view and FIG. 14is a rear perspective view of an apparatus 100 according to an exemplaryembodiment of the invention. The apparatus 100 includes a frame 102 andan enclosure 104. Much of the enclosure 104 is removed or showntransparent in FIGS. 12-14.

The apparatus 100 includes several of the same or similar components andfeatures as the apparatus described above in reference to FIG. 2.Referring to FIG. 12, a build chamber 106 is provided on a base plate108 that is connected to the frame 102. The build chamber 106 is definedby a wall or vat ring 110 and a build plate or “window” such as one ofthe windows described above in reference to FIGS. 2 and 6-11.

Turning to FIG. 13, a carrier 112 is driven in a vertical directionalong a rail 114 by a motor 116. The motor may be any suitable type ofmotor, such as a servo motor. An exemplary suitable motor is the NXM45Amotor available from Oriental Motor of Tokyo, Japan.

A liquid reservoir 118 is in fluid communication with the build chamber106 to replenish the build chamber 106 with liquid resin. For example,tubing may run from the liquid reservoir 118 to the build chamber 106. Avalve 120 controls the flow of liquid resin from the liquid reservoir118 to the build chamber 106. An exemplary suitable valve is apinch-style aluminum solenoid valve for tubing available fromMcMaster-Carr of Atlanta, Ga.

The frame 102 includes rails 122 or other some other mounting feature onwhich a light engine assembly 130 (FIG. 15) is held or mounted. A lightsource 124 is coupled to the light engine assembly 130 using a lightguide entrance cable 126. The light source 124 may be any suitable lightsource such as a BlueWave® 200 system available from Dymax Corporationof Torrington, Conn.

Turning to FIG. 15, the light engine or light engine assembly 130includes condenser lens assembly 132 and a digital light processing(DLP) system including a digital micromirror device (DMD) 134 and anoptical or projection lens assembly 136 (which may include an objectivelens). A suitable DLP system is the DLP Discovery™ 4100 system availablefrom Texas Instruments, Inc. of Dallas, Tex. Light from the DLP systemis reflected off a mirror 138 and illuminates the build chamber 106.Specifically, an “image” 140 is projected at the build surface orwindow.

Referring to FIG. 14, an electronic component plate or breadboard 150 isconnected to the frame 102. A plurality of electrical or electroniccomponents are mounted on the breadboard 150. A controller or processor152 is operatively associated with various components such as the motor116, the valve 120, the light source 124 and the light engine assembly130 described above. A suitable controller is the Propeller Proto Boardavailable from Parallax, Inc. of Rocklin, Calif.

Other electrical or electronic components operatively associated withthe controller 152 include a power supply 154 and a motor driver 158 forcontrolling the motor 116. In some embodiments, an LED light sourcecontrolled by pulse width modulation (PWM) driver 156 is used instead ofa mercury lamp (e.g., the Dymax light source described above).

A suitable power supply is a 24 Volt, 2.5 A, 60 W, switching powersupply (e.g., part number PSI-60W-24 (HF60W-SL-24) available from MarlinP. Jones & Assoc, Inc. of Lake Park, Fla.). If an LED light source isused, a suitable LED driver is a 24 Volt, 1.4 A LED driver (e.g., partnumber 788-1041-ND available from Digi-Key of Thief River Falls, Minn.).A suitable motor driver is the NXD20-A motor driver available fromOriental Motor of Tokyo, Japan.

The apparatus of FIGS. 12-15 has been used to produce an “image size” ofabout 75 mm by 100 mm with light intensity of about 5 mW/cm². Theapparatus of FIGS. 12-15 has been used to build objects at speeds ofabout 100 to 500 mm/hr. The build speed is dependent on light intensityand the geometry of the object.

Example 5 Another Example Embodiment of an Apparatus

FIG. 16 is a front perspective view of an apparatus 200 according toanother exemplary embodiment of the invention. The apparatus 200includes the same components and features of the apparatus 100 with thefollowing differences.

The apparatus 200 includes a frame 202 including rails 222 or othermounting feature at which two of the light engine assemblies 130 shownin FIG. 15 may be mounted in a side-by-side relationship. The lightengine assemblies 130 are configured to provide a pair of “tiled” imagesat the build station 206. The use of multiple light engines to providetiled images is described in more detail above.

The apparatus of FIG. 16 has been used to provide a tiled “image size”of about 150 mm by 200 mm with light intensity of about 1 mW/cm². Theapparatus of FIG. 16 has been used to build objects at speeds of about50 to 100 mm/hr. The build speed is dependent on light intensity and thegeometry of the object.

Example 6 Another Example Embodiment of an Apparatus

FIG. 18 is a front perspective view and FIG. 19 is a side view of anapparatus 300 according to another exemplary embodiment of theinvention. The apparatus 300 includes the same components and featuresof the apparatus 100 with the following differences.

The apparatus 300 includes a frame 302 including rails 322 or othermounting feature at which a light engine assembly 330 shown in FIG. 20may be mounted in a different orientation than the light assembly 130 ofthe apparatus 100. Referring to FIGS. 19 and 20, the light engineassembly 330 includes a condenser lens assembly 332 and a digital lightprocessing (DLP) system including a digital micromirror device (DMD) 334and an optical or projection lens assembly 336 (which may include anobjective lens). A suitable DLP system is the DLP Discovery™ 4100 systemavailable from Texas Instruments, Inc. of Dallas, Tex. Light from theDLP system illuminates the build chamber 306. Specifically, an “image”340 is projected at the build surface or window. In contrast to theapparatus 100, a reflective mirror is not used with the apparatus 300.

The apparatus of FIGS. 18-20 has been used to provide “image sizes” ofabout 10.5 mm by 14 mm and about 24 mm by 32 mm with light intensity ofabout 200 mW/cm² and 40 mW/cm² The apparatus of FIGS. 18-20 has beenused to build objects at speeds of about 10,000 and 4,000 mm/hr. Thebuild speed is dependent on light intensity and the geometry of theobject.

Example 7 Control Program with Lua Scripting

Current printer technology requires low level control in order to ensurequality part fabrication. Physical parameters such as light intensity,exposure time and the motion of the carrier should all be optimized toensure the quality of a part. Utilizing a scripting interface to acontroller such as the Parallax PROPELLER™ microcontroller using theprogramming language “Lua” provides the user with control over allaspects of the printer on a low level. See generally R. Ierusalimschy,Programming in Lua (2013) (ISBN-10: 859037985X; ISBN-13:978-8590379850).

This Example illustrates the control of a method and apparatus of theinvention with an example program written utilizing Lua scripting.Program code corresponding to such instructions, or variations thereofthat will be apparent to those skilled in the art, is written inaccordance with known techniques based upon the particularmicrocontroller used.

Concepts.

A part consists of slices of polymer which are printed continuously. Theshape of each slice is defined by the frame that is being displayed bythe light engine.

Frame.

The frame represents the final output for a slice. The frame is whatmanifests as the physical geometry of the part. The data in the frame iswhat is projected by the printer to cure the polymer.

Slice.

All the 2D geometry that will be outputted to a frame should be combinedin a Slice. Slices can consist of procedural geometry, Slices of a 3Dmodel or any combination of the two. The slice generating process allowsthe user to have direct control over the composition of any frame.

Slice of a 3D Model.

A slice is a special type of 2D geometry derived from a 3D model of apart. It represents the geometry that intersects a plane that isparallel to the window. Parts are usually constructed by taking 3Dmodels and slicing them at very small intervals. Each slice is theninterpreted in succession by the printer and used to cure the polymer atthe proper height.

Procedural Geometry.

Procedurally generated geometry can also be added to a slice. This isaccomplished by invoking shape generation functions, such as“addcircle”, “addrectangle”, and others. Each function allows projectionof the corresponding shape onto the printing window. A produced partappears as a vertically extruded shape or combination of shapes.

Coordinate Spaces: Stage.

The coordinate system that the stage uses is usually calibrated suchthat the origin is 1-20 microns above the window.

Coordinate Spaces: Slice.

Coordinate system of the projected slice is such that origin is locatedat the center of the print window.

Quick Start.

The following is the most basic method of printing a part from a sliced3D model. Printing a sliced model consists of 4 main parts: Loading thedata, preparing the printer, printing, and shutdown.

Loading Data.

In this section of the code the sliced model data is loaded into memory.The file path to the model is defined in the Constants section of thecode. See the full code below for details.

Loading Model

modelFilePath=“Chess King.svg”

numSIlces=loadslices(modelFilePath)

Preparing the printer it is important to do two things before printing.You must first turn on the light engine with the relay function, and ifapplicable, the desired fluid height should be set.

Prepare Printer

relay(true)—turn light on

showframe(−1)—ensure nothing is exposed during setup

setlevels(0.55, 0.6)—if available, printer set fluid pump to maintainabout 55% fill

Printing.

The first step of the printing process is to calibrate the system andset the stage to its starting position by calling gotostart. Next webegin a for loop in which we print each slice. The first line of the forloop uses the infoline command to display the current slice index in thesidebar. Next we determine the height at which the next slice should becured. That value is stored to nextHeight. Following this we move thestage to the height at which the next slice needs to be cured. To ensurea clean print it can sometimes be necessary to wait for oxygen todiffuse into the resin. Therefore we call sleep for a half second (theexact time for preExposureTime is defined in the constants section aswell). After this it's time to actually cure the resin so we callshowframe and pass it the index of the slice we want to print, which isstored in sliceIndex by the for loop. We sleep again after this forexposureTime seconds in order to let the resin cure. Before moving on tothe next frame, we call showframe(−1) in order to prevent the lightengine from curing any resin while the stage is moving to the nextheight.

Execute Print

gotostart( )--move stage to starting position for sliceIndex=0,numSlices−1 do infoline(5, string.format(“Current Slice: %d”,sliceIndex)) nextHeight = sliceheight(sliceIndex)--calculate the heightthat the stage should be at to expose this frame moveto(nextHeight,stageSpeed)--move to nextHeight sleep(preExposureTime)--wait a givenamount of time for oxygen to diffuse into resin , prepExposureTime ispredefined in the Constants section showframe(sliceIndex)--show frame toexpose sleep(exposureTime)--wait while frame exposes, exposureTime ispredefined in the Constants section showframe(−1)-- show nothing toensure no exposure while stage is moving to next position end

Shutdown.

The final step in the printing process is to shut down the printer. Callrelay(false) to turn the light engine off. If you are using fluidcontrol, call setlevels(0,0) to ensure the valve is shut off. Finally itis a good idea to move the stage up a bit after printing to allow foreasy removal of the part.

Shutdown

relay(false)setlevels(0,0)

Lift Stage to Remove Part

moveby(25, 16000)Fully completed code implementing instructions based on the above is setforth below.

Constants

exposureTime=1.5—in secondspreExposureTime=0.5—in secondsstageSpeed=300—in mm/hour

Loading Model

modelFilePath=“Chess King.svg”numSlices=loadslices(modelFilePath)

Calculating Parameters

maxPrintHeight=sliceheight(numSlices−1)—find the highest point in theprint, this is the same as the height of the last slice. Slices are 0indexed, hence the −1.infoline(1, “Current Print Info:”)infoline(2, string.format(“Calculated Max Print Height: % dmm”,maxPrintHeight))infoline(3, string.format(“Calculated Est. Time: % dmin”,(maxPrintHeight/stageSpeed)*60+(preExposureTime+exposureTime)*numSlices/60))infoline(4, string.format(“Number of Slices: % d”, numSlices))

Prepare Printer

relay(true)—turn light onshowframe(−1)—ensure nothing is exposed during setupsetlevels(0.55, 0.6)—if available, printer set fluid pump to maintainabout 55% fill

Execute Print

gotostart( )--move stage to starting position for sliceIndex=0,numSlices−1 do infoline(5, string.format(“Current Slice: %d”,sliceIndex)) nextHeight = sliceheight(sliceIndex)--calculate the heightthat the stage should be at to expose this frame moveto(nextHeight,stageSpeed)--move to nextHeight sleep(preExposureTime)--wait a givenamount of time for oxygen to diffuse into resin , prepExposureTime ispredefined in the Constants section showframe(sliceIndex)--show frame toexpose sleep(exposureTime)--wait while frame exposes, exposureTime ispredefined in the Constants section showframe(−1)-- show nothing toensure no exposure while stage is moving to next position end

Shutdown

relay(false)setlevels(0,0)

Lift Stage to Remove Part

moveby(25, 16000)

Gotostart

The main purpose of gotostart is to calibrate the stage. This functionresets the coordinate system to have the origin at the lowest point,where the limit switch is activated. Calling this command will move thestage down until the limit switch in the printer is activated; thisshould occur when the stage is at the absolute minimum height.

gotostart( ) moves stage to start at the maximum speed which varies fromprinter to printer.

gotostart( )—moving to origin at default speedgotostart(number speed) moves stage to start at speed given inmillimeters/hour.gotostart(15000)—moving stage to origin at 15000 mm/hr

speed: speed, in mm/hour, at which the stage will move to the startposition.

Moveto

moveto allows the user to direct the stage to a desired height at agiven speed.

Safe upper and lower limits to speed and acceleration are ensuredinternally.

moveto(number targetHeight, number speed)moveto(25, 15000)—moving to 25 mm at 15,000 mm/hrmoveto(number targetHeight, number speed, number acceleration)This version of the function allows an acceleration to be defined aswell as speed. The stage starts moving at initial speed and thenincreases by acceleration.moveto(25, 20000, 1e7)—moving the stage to 25 mm at 20,000 mm/hr whileaccelerating at 1 million mm/hr̂2moveto(number torgetHeight, number speed, table controlPoints, functioncallback)This function behaves similar to the basic version of the function. Itstarts at its initial speed and position and moves to the highest pointon the control point table. callback is called when the stage passeseach control point.

-   -   function myCallbackFunction(index)—defining the callback        function print(“hello”)    -   end    -   moveto(25, 20000, slicecontrolpoints( ),        myCallbackFunction)—moving the stage to 25 mm at 20,000 mm/hr        while calling myCallbackFunction at the control points generated        by slicecontrolpoints( )    -   moveto(number targetHeight, number speed, number acceleration,        table controlPoints, function callback) This function is the        same as above except the user can pass an acceleration. The        stage accelerates from its initial position continuously until        it reaches the last control point.    -   function myCallbackFunction(Index)—defining the callback        function print(“hello”)    -   end    -   moveto(25, 20000, 0.5e7, slicecontrolpoints( ),        myCallbackFunction)—moving the stage to 25 mm at 20,000 mm/hr        while accelerating at 0.5 million mm/hr̂2 and also calling        myCallbackFunction at the control points generated by        slicecontrolpoints( )    -   targetHeight height, in mm from the origin, that the stage will        move to.    -   initialSpeed: initial speed, in mm/hour, that the stage will        start moving at.    -   acceleration: rate, in mm/hour², that the speed of the stage        will increase from initial speed.    -   controlPoints: a table of target heights in millimeters. After        the stage reaches a target height, it calls the function        callback.    -   callback. pointer to a function that will be called when the        stage reaches a control point. The callback function should take        one argument which is the index of the control point the stage        has reached.        moveby

moveby allows the user to change the height of the stage by a desiredamount at a given speed. Safe upper and lower limits to speed andacceleration are ensured internally.

moveby(number dHeight, number initaolSpeed)

1 moveby(−2, 15000)—moving down 2 mm at 15,000 mm/hr

-   -   moveby(number dHeight, number initialSpeed, number acceleration)        This version of the function allows an acceleration to be        defined as well as speed. The stage starts moving at initial        speed and then increases by acceleration until it reaches its        destination.    -   1 moveby(25, 15000, 1e7)—moving up 25 mm at 15,000 mm/hr while        accelerating 1e7 mm/hr̂2    -   moveby(number dHeight, number initialSpeed, table controlPoints,        function callback) This function usage allows the user to pass        the function a table of absolute height coordinates. After the        stage reaches one of these target heights, it calls the function        ‘callback.’ Callback should take one argument which is the index        of the control point it has reached.        -   function myCallbackFunction(index)—defining the callback            function print(“hello”)    -   end    -   moveby(25, 20000, slicecontrolpoints( ),        myCallbackFunction)—moving the stage up 25 mm at 20,000 mm/hr        while calling myCallbackFunction at the control points generated        by slicecontrolpoints( )    -   moveby(number dHeight, number initialSpeed, number acceleration,        table controlPoints, function callback) This function is the        same as above except the user can pass an acceleration. The        stage accelerates from its initial position continuously until        it reaches the last control point.        -   function myCallbackFunction(index)—defining the callback            function print(“hello”)        -   end

moveby(25, 20000, 1e7,slicecontrolpoints( ), myCallbackFunction)—movingthe stage up 25 mm at 20,000 mm/hr while calling myCallbackFunction atthe control points generated by slicecontrolpoints( ) and acceleratingat 1e7 mm/hr̂2

-   -   dHeight: desired change in height, in millimeters, of the stage.    -   initialSpeed: initial speed, in mm/hour, at which the stage        moves.    -   acceleration: rate, in mm/hour², that the speed of the stage        will increase from initial speed.    -   controlPoints: a table of target heights in millimeters. After        the stage reaches a target height, it calls the function        callback.    -   callback: pointer to a function that will be called when the        stage reaches a control point. The callback function should take        one argument which is the index of the control point the stage        has reached.

Light Engine Control

light

-   -   relay is used to turn the light engine on or off in the printer.        The light engine must be on in order to print. Make sure the        relay is set to off at the end of the script relay(boolean        lighton)    -   relay(true)—turning light on    -   lightOn: false turns the light engine off, true turns the light        engine on.

Adding Procedural Geometry

-   -   Functions in this section exist to project shapes without using        a sliced part file. Every function in this section has an        optional number value called figureIndex. Each figure in a slice        has its own index. The figures reside one on top of another.        Figures are drawn so that the figure with the highest index is        ‘on top’ and will therefore not be occluded by anything below        it. By default indexes are assigned in the order that they are        created so the last figure created will be rendered on top. One        can, however, change the index by passing the desired index into        figureIndex.

Every function in this section requires a sliceIndex argument. Thisvalue is the index of the slice that the figure will be added to.

Note that generating this procedural geometry does not guarantee that itwill be visible or printable. One must use one of the functions such asfillmask or linemask outlined below.

addcircle

addcirde(number x, number y, number radius, number sliceindex) addcircledraws a circle in the specified slice slice.

addCirde(0,0, 5, 0)—creating a circle at the origin of the first slicewith a radius of 5 mm

-   -   x: is the horizontal distance, in millimeters, from the center        of the circle to the origin.    -   y: is the vertical distance, in millimeters, from the center of        the circle to the origin.    -   radius: is the radius of the circle measured in millimeters.    -   sliceIndex: index of the slice to which the figure will be        added.    -   Returns: figure index of the figure.        addrectangle    -   addrectangle(number x, number y, number width, number height        number sliceindex) addrectangle draws a rectangle in the        specified slice.        addrectangle(0,0, 5,5, 0)—creating a 5 mm×5 mm square with its        top left corner at the origin.    -   x: horizontal coordinate, in millimeters, of the top left corner        of the rectangle.    -   y: vertical coordinate, in millimeters, of the top left corner        of the rectangle.    -   width: width of the rectangle in millimeters.    -   height: height of the rectangle in millimeters.    -   sliceIndex: index of the slice to which the figure will be        added.    -   Returns: figure index of the figure.        addline    -   addline(number x0, number y0, number x1, number y1, number        sliceindex) addline draws a line segment.        addline(0,0, 20,20, 0)—creating a line from the origin to 20 mm        along the x and y axis on the first slice.    -   x0: horizontal coordinate of the first point in the segment,        measured in millimeters.    -   y0: vertical coordinate of the first point in the segment,        measured in millimeters.    -   x1: horizontal coordinate of the second point in the segment,        measured in millimeters.    -   y²: vertical coordinate of the second point in the segment,        measured in millimeters.    -   sliceIndex: index of the slice to which the figure will be        added. Returns: figure index of the figure.        addtext

text(number x, number y, number scale, string text, number sliceindex)addtext draws text on the specified slice starting at position ‘x, y’with letters of size ‘scale’.

addtext(0,0, 20, “Hello world”, 0)—writing Hello World at the origin ofthe first slice

-   -   x: horizontal coordinate, measured in millimeters, of the top        left corner of the bounding box around the text.    -   y: vertical coordinate, measured in millimeters, of the top left        corner of the bounding box around the text.    -   scale: letter size in millimeters, interpretation may vary        depending on the underlying operating system (Windows, OSX,        Linux, etc).    -   text: the actual text that will be drawn on the slice.    -   sliceIndex: index of the slice to which the figure will be        added. Returns: figure index of the figure.

2.4 Fill & Line Control

2.4.1 fillmask

-   -   fillmask(number color, number sliceindex, number figureIndex)        fillmask is used to control how the procedural geometry is        drawn. fillmask tells the figure in question to fill the        entirety of its interior with color.    -   color: can be any number on the range 0 to 255. Where 0 is black        and 255 is white, any value in between is a shade of grey        interpolated linearly between black and white based on the color        value. Any value less than 0 will produce a transparent color.

myCircle=addCircle(0,0,5,0)—creating the circle to fill

fillmask(255, 0, myCircle)—Creating a white filled circle

-   -   sliceIndex:the index of the slice that should be modified.    -   figureIndex:the is used to determine which figure on the slice        should be filled. Each figure has its own unique index. If no        figureIndex is passed, the fill applies to all figures in the        slice.

2.4.2 Linemask

-   -   linemask(number color, number sliceindex, number figureIndex)        linemask is used to control how the procedural geometry is        drawn. linemask tells a figure to draw its outline in a specific        color. The width of the outline is defined by the function        linewidth.

myCircle=addCircle(0,0,20,0)—creating the circle to fill

linemask(255, 0, myCircle)—setting the outline of the circle to be white

fillmask(150,0, myCircle)—setting the fill of the circle to be grey

-   -   color: can be any number on the range 0 to 255. Where 0 is black        and 255 is white, any value in between is a shade of grey        interpolated linearly between black and white based on the color        value. Any value less than 0 will produce a transparent color.    -   sliceIndex: the index of the slice that should be modified.    -   figureIndex: is used to determine which figure on the slice        should be filled.    -   Each figure has its own unique index. If no figureIndex is        passed, the fill applies to all figures in the slice.

2.43 linewidth

-   -   linewidth(number width, number sliceindex, number figureIndex)        linewidth is used to set the width of the line that linemask        will use to outline the figure.

linewidth(2,0)—setting the line width for every figure on the firstslice to 2 mm

-   -   sliceIndex: the index of the slice that should be modified.    -   figureIndex: is used to determine which figure on the slice        should have its outline changed. Each figure has its own unique        index, see section 2.3 (Pg. 10) for more details. If no        figureIndex is passed, the fill applies to all figures in the        slice.        loadmask    -   loadmask(string filepath) loadmask allows for advanced fill        control. It enables the user to load a texture from a bitmap        file and use it to fill the entirety of a figure with the        texture.    -   texture=loadmask(“voronoi_noise.png”)—loading texture.        voronoi_noise.png is in the same directory as the script.    -   myCircle=addCirde(0,0,20,0)—creating the circle to fill    -   fillmask(texture, 0, myCircle)—filling the circle with voronoi        noise    -   filepath: file path to image file    -   Returns: a special data type which can be passed into a fillmask        or    -   linemask function as the color argument.

Frames

showframe

-   -   showframe(number sliceindex) showframe is essential to the        printing process. This function sends the data from a slice to        the printer. Call showframes on a frame that doesn't exist to        render a black frame e.g. showframe(−1).

showframe(2)—showing the 3rd slice

-   -   sliceIndex: the index of the slice to send to the printer.        framegradient    -   framegradient(number slope) framegradient is designed to        compensate for differences in light intensity.        calcframe

calcframe( )

-   -   calcframe is designed to analyze the construction of a slice        calculates the last frame shown.    -   showframe(0)    -   calcframe( )    -   Returns: the maximum possible distance between any point in the        figure and the edge.

2.5.4 loadframe

loadframe(string filepath)

-   -   loadframe is used to load a single slice from a supported bitmap        file.

loadframe(“slice.png”)—slice.png is in the same directory as the script

-   -   filepath: file path to slice image.

Slices

addslice

-   -   addslice(number sliceHeight) addslice creates a new slice at a        given height at the end of the slice stack.

addslice(0.05)—adding a slice at 0.05 mm

addslice(number sliceHeight. number sliceIndex)

-   -   addslice(0.05, 2)—adding a slice at 0.05 mm and at index 2. this        pushes all layers 2 and higher up an index.    -   addslice creates a new slice at a given height and slice index.    -   sliceHeight: height, in millimeters, of the slice.    -   sliceIndex: index at which the slice    -   should be added. Returns: slice    -   index.

loadslices

-   -   loadslices(string filepath) loadslices is used to load all the        slices from a 2D slice file.

loadslices(“Chess King.svg”)—loading all the slices from the ChessKing.svg file

-   -   filepath: file path to the sliced model. Acceptable formats are        .cli and .svg. Returns: number of slices.        sliceheight    -   sliceheight(number sliceIndex) sliceheight is used to find the        height of a slice in mm off the base.

addslice(0.05,0)—setting the first slice to 0.05 mm

sliceheight(0)—checking the height of slice 0, in this example it shouldreturn 0.05

-   -   sliceIndex: index of the slice to check. Returns: slice height        in mm.2.6.4 slicecontrolpoints    -   slicecontrolpoints( ) slicecontrolpoints is a helper function        which creates a control point for each slice of a model. These        control points can be passed to the moveto or moveby function to        set it to callback when the stage reaches the height of each        slice. Make sure loadslices has been called prior to calling        this function.        loadslices(“Chess King.svg”)        controlPoints=slicecontrolpoints( )    -   Returns: Lua table of control points.

Timing Sleep

-   -   sleep(number seconds) sleep allows the user to pause the        execution of the program for a set number of seconds.        sleep(0.5)—sleeping for a half second    -   seconds: number of seconds to pause script execution.

Clock

-   -   clock( ) clock returns the current time in seconds. It is        accurate at least up to the millisecond and should therefore be        used instead of Lua's built in clock functionality. clock should        be used as a means to measure differences in time as the start        time for the second count varies from system to system.

t1=dock( )

loadslices(“Chess King.svg”)

deltaTime clock( )−t1

Returns: system time in seconds.

Fluid Control

This set of functions can be used with printer models that support fluidcontrol. Before the script finishes executing, setlevels(0,0) should becalled to ensure that the pump stops pumping fluid into the vat.

getcurrentlevel

-   -   getcurrentlevel( ) getcurrentlevel returns the percentage of the        vat that is full.

print(string.format(“Vat is % d percent full.”, getcurrentlevel( )*100))

-   -   Returns: a floating point number on the range 0 to 1 that        represents the percentage of the vat that is full.        setlevels    -   setlevels(number min, number max) setlevels allows the user to        define how much fluid should be in the vat. The fluid height        will be automatically regulated by a pump. The difference        between min and max should be greater than 0.05 to ensure that        the valve is not constantly opening and closing.

setlevels(0.7,0.75)—keeping vat about 75 percent full

min: the minim percentage of the vat that should be full. Entered as afloating point number from 0 to 1.

-   -   max: the max percentage of the vat that should be full. Entered        as a floating point number from 0 to 1.

User Feedback

2.9.1 infoline

-   -   infoline(int lineindex, string text) infoline allows the user to        display up to 5 lines of text in a constant position on the        sidebar of the Programmable Printer Platform. This function is        often used to allow the user to monitor several changing        variables at once.

infoline(1, string.format(“Vat is % d percent full.”, getcurrentlevel()100))

-   -   lineIndex: the index of the line. Indexes should be in the range        1 to 5, 1 being the upper most line. text: text to be displayed        at line index.

Global Configuration Table.

Before a print script is executed, all global variables are loaded intoa configuration table called cfg. Most of the data in this table hasalready been read by the Programmable Printer Platform by the time theusers script executes, therefore, changing them will have no effect.However, writing to the xscale, yscale, zscale, xorig and yorig fieldsof the cfg, will effect all the loadslices and addlayer calls that aremade afterwards. If the users script is designed to be run at a specificscale and/or position, it is good practice to override the cfg with thecorrect settings to ensure the scale and position can't be accidentallychanged by the Programmable Printer Platform.

cfg.xscale=3—overriding global settings to set scale on the x axis to 3cfg.yscale=2—overriding global settings to set scale on the y axis to 2cfg.zscale=1—overriding global settings to set scale on the z axis to 1cfg.xorig=−2.0—overriding global settings to set the origin on the xaxis 2 mm leftcfg.yorig=0.25—overriding global settings to set the origin on the yaxis 0.25 mm in the positive direction

Fields in cfg:

serial port: name of serial port (changing this variable wont effectcode)

xscale: x scale yscale: y scale

zscale: z scale

xorig: x origin yorig: y origin

hw xscale: pixel resolution in x direction (changing this variable won'teffect code)

hw yscale: pixel resolution in y direction (changing this variable won'teffect code)

Useful Lua Standard Libraries.

The math standard library contains several different functions that areuseful in calculating geometry. The string object is most useful inprinting for manipulating info strings. For details contact LabLua atDepartamento de Informatica, PUC-Rio, Rua Marquês de São Vicente, 225;22451-900 Rio de Janeiro, RJ, Brazil

Example 8 Lua Script Program for Continuous Print

This example shows a Lua script program corresponding to Example 7 abovefor continuous three dimension printing.

Constants

sliceDepth=0.05—in millimeters

exposureTime=0.225—in seconds

Loading Model

modelFilePath=“Chess King.svg”

numSlilces=loadslices(modelFilePath)

controlPoints=slicecontrolpoints( )—Generate Control Points

Calculating Parameters

exposureTime = exposureTime/(60*60)--converted to hours stageSpeed =sliceDepth/exposureTime--required distance/required time maxPrintHeight= sliceheight(numSlices−1)--find the highest point in the print, this isthe same as the height of the last slice. Slices are 0 indexed, hencethe −1. infoline(1, “Current Print Info:”) infoline(2,string.format(“Calulated Stage Speed: %dmm/hr\n”, stageSpeed))infoline(3, string.format(“Calculated Max Print Height: %dmm”,maxPrintHeight)) infoline(4, string.format(“Calculated Est. Time:%dmin”, (maxPrintHeight/stageSpeed)*60)) --Create Callback Function foruse with moveto function movetoCallback(controlPointIndex)showframe(controlPointIndex) end

Prepare Printer

relay(true)—turn light on

setlevels(0.55, 0.6)—if available, printer set fluid pump to maintainabout 50% fill

Execute Print

gotostart( )—move stage to starting position

moveto(maxPrintHeight, stageSpeed, controlPoints, movetoCallback)

Shutdown

relay(false)

setlevels(0,0)

Lift Stage to Remove Part

moveby(25, 160000)

Example 9 Lua Script Program for Cylinder and Buckle

This example shows a Lua script program for two fitted parts that useprocedural geometry.

Cylinder:

Constants

exposureTime=1.5—in seconds

preExposureTime=1—in seconds

stageSpeed=300—in mm/hour

sliceDepth=0.05

numSlices=700

Generating Model

radius = 11 thickness = 4 smallCircleRad = 1.4 for sliceIndex =0,numSlices−1 do addlayer(sliceDepth*(sliceIndex+1), sliceIndex)--thedepth of a slice*its index = height of slice largeCircle =addcircle(0,0,radius, sliceIndex) linewidth(thickness, sliceIndex,largeCircle) linemask(255, sliceIndex, largeCircle) for i=0,2*math.pi,2*math.pi/8 do addcircle(math.cos(i)*radius, math.sin(i)*radius,smallCircleRad, sliceIndex) end fillmask(0,sliceIndex) end

calculating parameters

-   -   maxPrintHeight=sliceheight(numSlices−1)—find the highest point        in the print, this is the same as the height of the last slice.        Slices are 0 indexed, hence the −1.    -   infoline(1, “Current Print Info:”)    -   infoline(2, string.format(“Calculated Max Print Height: % dmm”,        maxPrintHeight))    -   infoline(3, string.format(“Calculated Est. Time: % dmin”,        (maxPrintHeight/stageSpeed)*60+(preExposureTime+exposureTime)*numSlices/60))    -   infoline(4, string.format(“Number of Slices: % d”, numSlices))

Prepare Printer

relay(true)—turn light on

showframe(−1)—ensure nothing is exposed during setup

setlevels(0.55, 0.6)—if available, printer set fluid pump to maintainabout 55% fill

Execute Print

gotostart( )--move stage to starting position for sliceIndex=0,numSlices−1 do infoline(5, string.format(“Current Slice: %d”,sliceIndex)) nextHeight = sliceheight(sliceIndex)--calculate the heightthat the stage should be at to expose this frame moveto(nextHeight,stageSpeed)--move to nextHeight sleep(preExposureTime)--wait a givenamount of time for oxygen to diffuse into resin , prepExposureTime ispredefined in the Constants section showframe(sliceIndex)--show frame toexpose sleep(1.5)--wait while frame exposes, exposureTime is predefinedin the Constants section showframe(−1)-- show nothing to ensure noexposure while stage is moving to next position end

Shutdown

relay(false)

setlevels(0,0)

Lift Stage to Remove Part

moveby(25, 160000)

Buckle:

Constants

exposureTime=1.5—in seconds

preExposureTime=0.5—in seconds

stageSpeed=300—in mm/hour

sliceDepth=0.05

numSlices=900

Generating Model

 baseRadius = 11  thickness = 3  innerCircleRad = 7.5 for sliceIndex =0,numSlices−1 do addlayer(sliceDepth*sliceIndex+1))--the depth of aslice*its index = height of slice  if(sliceIndex < 100) then --baseaddcircle(0,0, baseRadius, sliceIndex) fillmask(255, sliceIndex)  else-- inner circle innerCircle = addcircle(0,0, innerCircleRad, sliceIndex)linewidth(thickness, sliceIndex, innerCircle) linemask(255, sliceIndex,innerCircle) for i = 0,4*2*math.pi/8, 2*math.pi/8 do  x =math.cos(i)*(innerCircleRad+thickness)  y =math.sin(i)*(innerCircleRad+thickness)  cutLine = addline(x,y, −x,−y,sliceIndex)  linewidth(3, sliceIndex, cutLine)  linemask(0, sliceIndex,cutLine)  end if (sliceIndex > 800) then --tips r0 = innerCircleRad +2if(sliceIndex < 850) then r0 = innerCircleRad + (sliceIndex−800)*(2/50) end  for i = 0,4*2*math.pi/8, 2*math.pi/8 do ang = i + (2*math.pi/8)/2x = math.cos(ang)*(r0) y = math.sin(ang)*(r0) nubLine = addline(x,y,−x,−y, sliceIndex) linewidth(2, sliceIndex, nubLine) linemask(255,sliceIndex, nubLine)  end fillmask(0,sliceIndex, addcircle(0,0,innerCircleRad−(thickness/2),  sliceIndex)) end endshowframe(sliceIndex) sleep(.02) end

Calculating Parameters

-   -   maxPrintHeight=sliceheight(numSlices−1)—find the highest point        in the print, this is the same as the height of the last slice.        Slices are 0 Indexed, hence the −1.    -   infoline(1, “Current Print Info:”)    -   infoline(2, string.format(“Calculated Max Print Height: % dmm”,        maxPrintHeight))    -   infoline(3, string.format(“Calculated Est. Time: % dmin”,        (maxPrintHeight/stageSpeed)*60+(preExposureTime+exposureTime)*numSlices/60))    -   infoline(4, string.format(“Number of Slices: % d”, numSlices))

Prepare Printer

relay(true)—turn light on

showframe(−1)—ensure nothing is exposed during setup

setlevels(0.55, 0.6)—if available, printer set fluid pump to maintainabout 55% fill

Execute Print

gotostart( )--move stage to starting position for sliceIndex=0,numSlices−1 do infoline(5, string.format(“Current Slice: %d”,sliceIndex)) nextHeight = sliceheight(sliceIndex)--calculate the heightthat the stage should be at to expose this frame moveto(nextHeight,stageSpeed)--move to nextHeight sleep(preExposureTime)--wait a givenamount of time for oxygen to diffuse into resin, prepExposureTime ispredefined in the Constants section showframe(sliceIndex)--show frame toexpose sleep(1.5)--wait while frame exposes, exposureTime is predefinedin the Constants section  showframe(−1)-- show nothing to ensure noexposure while stage is moving to next position end

Shutdown

relay(false)

setlevels(0,0)

Lift Stage to Remove Part

moveby(25, 16000)

Example 10 Continuous Fabrication with Intermittent Irradiation andAdvancing

A process of the present invention is illustrated in FIG. 21, where thevertical axis illustrates the movement of the carrier away from thebuild surface. In this embodiment, the vertical movement or advancingstep (which can be achieved by driving either the carrier or the buildsurface, preferably the carrier), is continuous and unidirectional, andthe irradiating step is carried out continuously. Polymerization of thearticle being fabricated occurs from a gradient of polymerization oractive surface, and hence creation of “layer by layer” fault lineswithin the article is minimized.

An alternate embodiment of the present invention is illustrated in FIG.22. In this embodiment, the advancing step is carried out in astep-by-step manner, with pauses introduced between active advancing ofthe carrier and build surface away from one another. In addition, theirradiating step is carried out intermittently, in this case during thepauses in the advancing step. We find that, as long as the inhibitor ofpolymerization is supplied to the dead zone in an amount sufficient tomaintain the dead zone and the adjacent gradient of polymerization oractive surface during the pauses in irradiation and/or advancing, thegradient of polymerization is maintained, and the formation of layerswithin the article of manufacture is minimized or avoided. Stateddifferently, the polymerization is continuous, even though theirradiating and advancing steps are not. Sufficient inhibitor can besupplied by any of a variety of techniques, including but not limitedto: utilizing a transparent member that is sufficiently permeable to theinhibitor, enriching the inhibitor (e.g., feeding the inhibitor from aninhibitor-enriched and/or pressurized atmosphere), etc. In general, themore rapid the fabrication of the three-dimensional object (that is, themore rapid the cumulative rate of advancing), the more inhibitor will berequired to maintain the dead zone and the adjacent gradient ofpolymerization.

Example 11 Continuous Fabrication with Reciprocation During Advancing toEnhance Filling of Build Region with Polymerizable Liquid

A still further embodiment of the present invention is illustrated inFIG. 23. As in Example 10 above, this embodiment, the advancing step iscarried out in a step-by-step manner, with pauses introduced betweenactive advancing of the carrier and build surface away from one another.Also as in Example 10 above, the irradiating step is carried outintermittently, again during the pauses in the advancing step. In thisexample, however, the ability to maintain the dead zone and gradient ofpolymerization during the pauses in advancing and irradiating is takenadvantage of by introducing a vertical reciprocation during the pausesin irradiation.

We find that vertical reciprocation (driving the carrier and buildsurface away from and then back towards one another), particularlyduring pauses in irradiation, serves to enhance the filling of the buildregion with the polymerizable liquid, apparently by pullingpolymerizable liquid into the build region. This is advantageous whenlarger areas are irradiated or larger parts are fabricated, and fillingthe central portion of the build region may be rate-limiting to anotherwise rapid fabrication.

Reciprocation in the vertical or Z axis can be carried out at anysuitable speed in both directions (and the speed need not be the same inboth directions), although it is preferred that the speed whenreciprocating away is insufficient to cause the formation of gas bubblesin the build region.

While a single cycle of reciprocation is shown during each pause inirradiation in FIG. 23, it will be appreciated that multiple cycles(which may be the same as or different from one another) may beintroduced during each pause.

As in Example 10 above, as long as the inhibitor of polymerization issupplied to the dead zone in an amount sufficient to maintain the deadzone and the adjacent gradient of polymerization during thereciprocation, the gradient of polymerization is maintained, theformation of layers within the article of manufacture is minimized oravoided, and the polymerization/fabrication remains continuous, eventhough the irradiating and advancing steps are not.

Example 12 Acceleration During Reciprocation Upstroke and DecelerationDuring Reciprocation Downstroke to Enhance Part Quality

We observe that there is a limiting speed of upstroke, and correspondingdownstroke, which if exceeded causes a deterioration of quality of thepart or object being fabricated (possibly due to degradation of softregions within the gradient of polymerization caused by lateral shearforces a resin flow). To reduce these shear forces and/or enhance thequality of the part being fabricated, we introduce variable rates withinthe upstroke and downstroke, with gradual acceleration occurring duringthe upstroke and gradual deceleration occurring during the downstroke,as schematically illustrated in FIG. 24.

Example 13 Fabrication in Multiple Zones

FIG. 25 schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object bymethods as described above, through a first base (or “adhesion”) zone,an optional second transition zone, and a third body zone. The overallprocess of forming the three-dimensional object is thus divided intothree (or two) immediately sequential segments or zones. The zones arepreferably carried out in a continuous sequence without pausesubstantial delay (e.g., greater than 5 or 10 seconds) between the threezones, preferably so that the gradient of polymerization is notdisrupted between the zones.

The first base (or “adhesion”) zone includes an initial light orirradiation exposure at a higher dose (longer duration and/or greaterintensity) than used in the subsequent transition and/or body zones.This is to obviate the problem of the carrier not being perfectlyaligned with the build surface, and/or the problem of variation in thepositioning of the carrier from the build surface, at the start of theprocess, by insuring that the resin is securely polymerized to thecarrier. Note an optional reciprocation step (for initial distributingor pumping of the polymerizable liquid in or into the build region) isshown before the carrier is positioned in its initial, start, position.Note that a release layer (not shown) such as a soluble release layermay still be included between the carrier and the initial polymerizedmaterial, if desired. In general, a small or minor portion of thethree-dimensional object is produced during this base zone (e.g., lessthan 1, 2 or 5 percent by volume). Similarly, the duration of this basezone is, in general, a small or minor portion of the sum of thedurations of the base zone, the optional transition zone, and the bodyzone (e.g., less than 1, 2 or 5 percent).

Immediately following the first base zone of the process, there isoptionally (but preferably) a transition zone. In this embodiment, theduration and/or intensity of the illumination is less, and thedisplacement of the oscillatory step less, compared to that employed inthe base zone as described above. The transition zone may (in theillustrated embodiment) proceed through from 2 or 5, up to 50 or moreoscillatory steps and their corresponding illuminations. In general, anintermediate portion (greater than that formed during the base zone, butless than that formed of during the body zone), of the three dimensionalobject is produced during the transition zone (e.g., from 1, 2 or 5percent to 10, 20 or 40 percent by volume). Similarly, the duration ofthis transition zone is, in general, greater than that of the base zone,but less than that of the body zone (e.g., a duration of from 1, 2 or 5percent to 10, 20 or 40 percent that of the sum of the durations of thebase zone, the transition zone, and the body zone (e.g., less than 1, 2or 5 percent).

Immediately following the transition zone of the process (or, if notransition zone is included, immediately following the base zone of theprocess), there is a body zone, during which the remainder of thethree-dimensional object is formed. In the illustrated embodiment, thebody zone is carried out with illumination at a lower dose than the basezone (and, if present, preferably at a lower dose than that in thetransition zone), and the reciprocation steps are (optionally but insome embodiments preferably) carried out at a smaller displacement thanthat in the base zone (and, if present, optionally but preferably at alower displacement than in the transition zone). In general, a majorportion, typically greater than 60, 80, or 90 percent by volume, of thethree-dimensional object is produced during the transition zone.Similarly, the duration of this body zone is, in general, greater thanthat of the base zone and/or transition zone (e.g., a duration of atleast 60, 80, or 90 percent that of the sum of the durations of the basezone, the transition zone, and the body zone).

Note that, in this example, the multiple zones are illustrated inconnection with an oscillating mode of fabrication, but the multiplezone fabrication technique described herein may also be implemented withother modes of fabrication as illustrated further in the examples below(with the transition zone illustrated as included, but again beingoptional).

Example 14 Fabrication with Intermittent (or “Strobe”) Illumination

The purpose of a “strobe” mode of operation is to reduce the amount oftime that the light or radiation source is on or active (e.g., to notmore than 80, 70, 60, 50, 40, or 30 percent of the total time requiredto complete the fabrication of the three-dimensional object), andincrease the intensity thereof (as compared to the intensity requiredwhen advancing is carried out at the same cumulative rate of speedwithout such reduced time of active illumination or radiation), so thatthe overall dosage of light or radiation otherwise remains substantiallythe same. This allows more time for resin to flow into the build regionwithout trying to cure it at the same time. The strobe mode techniquecan be applied to any of the existing general modes of operationdescribed herein above, including continuous, stepped, and oscillatorymodes, as discussed further below.

FIG. 26A schematically illustrates one embodiment of continuous mode. Inthe conventional continuous mode, an image is projected and the carrierstarts to move upwards. The image is changed at intervals to representthe cross section of the three-dimensional object being producedcorresponding to the height of the build platform. The speed of themotion of the build platform can vary for a number of reasons. Asillustrated, often there is a base zone where the primary goal is toadhere the object to the build platform, a body zone which has a speedwhich is suitable for the whole object being produced, and a transitionzone which is a gradual transition from the speed and/or dosages of thebase zone to the speeds and/or dosages of the body zone. Note that cureis still carried out so that a gradient of polymerization, whichprevents the formation of layer-by-layer fault lines, in thepolymerizable liquid in the build region, is preferably retained, andwith the carrier (or growing object) remaining in liquid contact withthe polymerizable liquid, as discussed above.

FIG. 26B schematically illustrates one embodiment of strobe continuousmode. In strobe continuous the light intensity is increased but theimage is projected in short flashes or intermittent segments. Theincreased intensity allows the resin to cure more quickly so that theamount of flow during cure is minimal. The time between flashes letsresin flow without being cured at the same time. This can reduceproblems caused by trying to cure moving resin, such as pitting.

In addition, the reduced duty cycle on the light source which isachieved in strobe mode can allow for use of increased intermittentpower. For example: If the intensity for the conventional continuousmode was 5 mW/cm² the intensity could be doubled to 10 mW/cm² and thetime that the image is projected could be reduced to half of the time,or the intensity could be increased 5-fold to 25 mW/cm² and the timecould be reduced to ⅕^(th) of the previous light on time.

FIG. 27A schematically illustrates one embodiment of stepped mode: Inthe conventional stepped mode an image is projected while the buildplatform is stationary (or moving slowly as compared to more rapidmovement in between illumination). When one height increment issufficiently exposed the image is turned off and the build platform ismoved upwards by some increment. This motion can be at one speed or thespeed can vary such as by accelerating from a slow speed when thethickness of uncured resin is thin to faster as the thickness of theuncured resin is thicker. Once the build platform is in the new positionthe image of the next cross section is projected to sufficiently exposethe next height increment.

FIG. 27B schematically illustrates one embodiment of strobe steppedmode: In the strobe stepped mode the light intensity is increased andthe amount of time that the image is projected is reduced. This allowsmore time for resin flow so the overall speed of the print can bereduced or the speed of movement can be reduced. For example: If theintensity for the conventional stepped mode was 5 mW/cm² and the buildplatform moves in increments of 100 um in 1 second and the image isprojected for 1 second the intensity could be doubled to 10 mW/cm², thetime that the image is projected could be reduced to 0.5 seconds, andthe speed of movement could be reduced to 50 um/second, or the time thatthe stage is moving could be reduced to 0.5 seconds. The increasedintensity could be as much as 5 fold or more allowing the time allottedfor image projection to be reduced to ⅕^(th) or less.

FIG. 28A schematically illustrates one embodiment of oscillatory mode:In the oscillatory mode an image is again projected while the buildplatform is stationary (or moving slowly as compared to more rapidmovement in-between illuminations). When one height increment is curedthe image is turned off and the build platform is moved upwards to pulladditional resin into the build zone and then moved back down to thenext height increment above the last cured height. This motion can be atone speed or the speed can vary such as by accelerating from a slowspeed when the thickness of uncured resin is thin to faster as thethickness of the uncured resin is thicker. Once the build platform is inthe new position the image of the next cross section is projected tocure the next height increment.

FIG. 28B illustrates one embodiment of strobe oscillatory mode. In thestrobe oscillatory mode the light intensity is increased and the amountof time that the image is projected is reduced. This allows more timefor resin flow so the overall speed of the print can be reduced or thespeed of movement can be reduced. For example: If the intensity for theconventional oscillatory mode was 5 mW/cm² and the build platform movesup by 1 mm and back down to an increment of 100 um above the previousheight in 1 second and the image is projected for 1 second the intensitycould be doubled to 10 mW/cm², the time that the image is projectedcould be reduced to 0.5 seconds, and the speed of movement could bereduced to by half or the time that the stage is moving could be reducedto 0.5 seconds. The increased intensity could be as much as 5 fold ormore allowing the time allotted for image projection to be reduced to⅕^(th) or less. Segment “A” of FIG. 29 is discussed further below.

FIG. 29A illustrates a segment of a fabrication method operated inanother embodiment of strobe oscillatory mode. In this embodiment, theduration of the segment during which the carrier is static is shortenedto close that of the duration of the strobe illumination, so that theduration of the oscillatory segment may—if desired—be lengthened withoutchanging the cumulative rate of advance and the speed of fabrication.

FIG. 29B illustrates a segment of another embodiment of strobeoscillatory mode, similar to that of FIG. 29, except that the carrier isnow advancing during the illumination segment (relatively slowly, ascompared to the upstroke of the oscillatory segment).

Example 15 Varying of Process Parameters During Fabrication

In the methods of Example 13-14, the operating conditions during thebody zone are shown as constant throughout that zone. However, variousparameters can be altered or modified in the course of the body zone, asdiscussed further below.

A primary reason for altering a parameter during production would bevariations in the cross section geometry of the three-dimensionalobject; that is, smaller (easier to fill), and larger (harder to fill)segments or portions of the same three-dimensional object. For easier tofill segments (e.g., 1-5 mm diameter equivalents), the speed of upwardsmovement could be quick (up to 50-1000 m/hr) and/or the pump heightcould be minimal (e.g., as little at 100 to 300 um). For larger crosssectional segments (e.g., 5-500 mm diameter equivalents) the speed ofupward movement can be slower (e.g., 1-50 mm/hr) and/or the pump heightcan be larger (e.g., 500 to 5000 um). Particular parameters will, ofcourse, vary depending on factors such as illumination intensity, theparticular polymerizable liquid (including constituents thereof such asdye and filler concentrations), the particular build surface employed,etc.

In some embodiments, the overall light dosage (determined by time andintensity) may be reduced as the “bulk” of the cross section beingilluminated increases. Said another way, small points of light may needhigher per unit dosage than larger areas of light. Without wishing to bebound to any specific theory, this may relate to the chemical kinematicsof the polymerizable liquid. This effect could cause us to increase theoverall light dosage for smaller cross sectional diameter equivalents.

In some embodiments, vary the thickness of each height increment betweensteps or pumps can be varied. This could be to increase speed withdecreased resolution requirements (that is, fabricating a portion thatrequires less precision or permits more variability, versus a portion ofthe object that requires greater precision or requires more precise ornarrow tolerances). For example, one could change from 100 um incrementsto 200 um or 400 um increments and group all the curing for theincreased thickness into one time period. This time period may beshorter, the same or longer than the combined time for the equivalentsmaller increments.

In some embodiments, the light dosage (time and/or intensity) deliveredcould be varied in particular cross sections (vertical regions of theobject) or even in different areas within the same cross section orvertical region. This could be to vary the stiffness or density ofparticular geometries. This can, for example, be achieved by changingthe dosage at different height increments, or changing the grayscalepercentage of different zones of each height increment illumination.

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

1. A method of forming a three-dimensional object, comprising: providinga carrier and an optically transparent member having a build surface,said carrier and said build surface defining a build regiontherebetween; filling said build region with a polymerizable liquid,continuously or intermittently irradiating said build region with lightthrough said optically transparent member to form a solid polymer fromsaid polymerizable liquid, continuously or intermittently advancing saidcarrier away from said build surface to form said three-dimensionalobject from said solid polymer, said filling step further comprisingvertically reciprocating said carrier with respect to said build surfaceto enhance or speed the refilling of said build region with saidpolymerizable liquid.
 2. The method of claim 1, wherein said filling,irradiating, and/or advancing steps are carried out while alsoconcurrently: (i) continuously maintaining a dead zone of polymerizableliquid in contact with said build surface, and (ii) continuouslymaintaining a gradient of polymerization zone between said dead zone andsaid solid polymer and in contact with each thereof, said gradient ofpolymerization zone comprising said polymerizable liquid in partiallycured form.
 3. The method of claim 2, wherein said optically transparentmember comprises a semipermeable member, and said continuouslymaintaining a dead zone is carried out by feeding an inhibitor ofpolymerization through said optically transparent member in an amountsufficient to maintain said dead zone and said gradient ofpolymerization.
 4. The method of claim 3, wherein said opticallytransparent member is comprised of a fluoropolymer.
 5. The method ofclaim 2, wherein said gradient of polymerization zone is maintained fora time of at least 1 minute.
 6. The method of claim 1, wherein saidvertically reciprocating is carried by motion of said carrier alone. 7.The method of claim 1, wherein said vertically reciprocating is carriedout by combined motion of said carrier and said build surface.
 8. Themethod of claim 1, wherein said irradiating is intermittent irradiating,and said intermittent irradiating is either (a) synchronized with saidvertically reciprocating, or (b) non-synchronized with said verticallyreciprocating.
 9. The method of claim 1, wherein said verticallyreciprocating step comprises an upstroke and a downstroke, with thedistance of said upstroke greater than the distance of said downstroke,to thereby concurrently carry out said advancing step in part or inwhole.
 10. The method of claim 1, wherein said vertically reciprocatingstep comprises an upstroke, and wherein the speed of said upstrokeaccelerates over a period of time during said upstroke.
 11. The methodof claim 10, wherein said upstroke begins gradually.
 12. The method ofclaim 1, wherein said vertically reciprocating step comprises adownstroke, and wherein the speed of said downstroke decelerates over aperiod of time during said downstroke.
 13. The method of claim 12,wherein said downstroke ends gradually.
 14. The method of claim 1,wherein said vertically reciprocating step is carried out over a totaltime of from 0.01 to 10 seconds, and/or over an upstroke distance oftravel of from 0.02 millimeters to 10 millimeters.
 15. The method ofclaim 1, wherein said advancing is carried out intermittently at a rateof 1 individual advances per minute up to 1000 individual advances perminute, each followed by a pause during which an irradiating step iscarried out.
 16. The method of claim 15, wherein each of said individualadvances is carried out over an average distance of travel for eachadvance of from 10 microns to 200 microns.
 17. The method of claim 1,wherein said build surface is fixed and stationary in the lateral (or Xand Y) dimensions.
 18. The method of claim 1, wherein said build surfaceis fixed and stationary in the vertical (or Z) dimension.
 19. The methodof claim 2, wherein said gradient of polymerization zone and said deadzone together have a thickness of from 1 to 1000 microns.
 20. The methodof claim 2, further comprising the step of disrupting said gradient ofpolymerization zone for a time sufficient to form a cleavage line insaid three-dimensional object.
 21. The method of claim 1, furthercomprising the step of heating said polymerizable liquid to reduce theviscosity thereof in said build region.
 22. The method of claim 3,wherein: said polymerizable liquid comprises a free radicalpolymerizable liquid and said inhibitor comprises oxygen; or saidpolymerizable liquid comprises an acid-catalyzed or cationicallypolymerizable liquid, and said inhibitor comprises a base.
 23. Anapparatus for forming a three-dimensional object from a polymerizableliquid, comprising: (a) a support; (b) a carrier operatively associatedwith said support on which carrier said three-dimensional object isformed; (c) an optically transparent member having a build surface, withsaid build surface and said carrier defining a build regiontherebetween; (d) a liquid polymer supply operatively associated withsaid build surface and configured to supply liquid polymer into saidbuild region for solidification or polymerization; (e) a radiationsource configured to irradiate said build region through said opticallytransparent member to form a solid polymer from said polymerizableliquid; (f) optionally at least one drive operatively associated witheither said transparent member or said carrier; (g) a controlleroperatively associated with said carrier, and/or optionally said atleast one drive, and said radiation source for advancing said carrieraway from said build surface to form said three-dimensional object fromsaid solid polymer, said controller further configured to oscillate orreciprocate said carrier with respect to said build surface to enhanceor speed the refilling of said build region with said polymerizableliquid.
 24. The apparatus of claim 23, said controller furtherconfigured to form said three-dimensional object from said solid polymerwhile also concurrently with said filling, advancing, and/or irradiatingstep: (i) continuously maintaining a dead zone of polymerizable liquidin contact with said build surface, and (ii) continuously maintaining agradient of polymerization zone between said dead zone and said solidpolymer and in contact with each thereof, said gradient ofpolymerization zone comprising said polymerizable liquid in partiallycured form
 25. The apparatus of claim 23, wherein the build surface issubstantially fixed or stationary.
 26. The apparatus of claim 24,wherein: said optically transparent member comprises a semipermeablemember: said semipermeable member comprises a top surface portion, abottom surface portion, and an edge surface portion; said build surfaceis on said top surface portion; and a feed surface is on at least one ofsaid top surface portion, said bottom surface portion, and said edgesurface portion.
 27. The apparatus of claim 24, wherein said opticallytransparent member comprises a semipermeable member.
 28. The apparatusof claim 27, wherein: said semipermeable member has a thickness of from0.1 to 100 millimeters; and/or wherein said semipermeable member has apermeability to oxygen of at least 7.5×10⁻¹⁷ m² s⁻¹ Pa⁻¹ (10 Barrers).29. The apparatus of claim 27, wherein said semipermeable member iscomprised of a fluoropolymer.